Aly E Abo-Amer | Sohag University (original) (raw)

Papers by Aly E Abo-Amer

ROMANIAN ARCHIVES, 1971

The presence of the specific antibodies for some enterobacteria -Yersinia, Salmonella and Shigell... more The presence of the specific antibodies for some enterobacteria -Yersinia, Salmonella and Shigella was investigated in patients hospitalized in the period 2000 -2007 with reactive arthritis and other rheumatoid diseases. The antibacterial antibodies in the diagnosis titres were found in 172 out of 1102 (15.6 %) patients. Increased antibodies levels to Yersinia were detected in the sera from 113 (65.7 %) of the 172 patients, for Shigella in 47 (27.3 %) and for Salmonella in 12 (7.0 %) cases. From all serologically positive patients 126 (73.2 %) had clinical diagnosis of reactive arthritis and 46 (26.7%) other rheumatoid diseases (ankylosing spondilytis, Reiter's syndrome, sacroilitis). The most serologically positive cases (63.9 %) were of middle-age (30-50 years). There were no significant differences between sexes among serologically positive cases. ABSTRACT Growth of Lactobacillus plantarum AA135 in MRS broth at 30 o C yielded maximal plantaricin AA13 activity of 10000 AU/ml at pH 3.8 after 16 hours. Maximal activity (10000 AU/ml) of plantaricin AA13 was recorded in MRS broth at initial pH of 5 or 5.5. Optimal production (10000 AU/ml) was recorded in the presence of tryptone (20 g/l), a combination of tryptone plus meat extract (1:0.6) or tryptone with yeast extract (1:0.6) as sole nitrogen source. Growth of Lactobacillus plantarum AA135 in the presence of 20 g/l glucose yielded bacteriocin activity of 10000 AU/ml. Moreover, when 40 g/l glucose was added, the plantaricin AA13 levels doubled to 20000 AU/ml. Concentrations of 5, 10 and 20 g/l K 2 HPO 4 lowered bacteriocin activity by 60 %. Supplementing MRS with 1 g/l or more glycerol repressed bacteriocin production. Maximal activity of 20000 AU/ml was recorded in MRS supplemented with Vitamin DL-6,8-thioctic acid. ABSTRACT Introduction. The emergence of the bacterial antibiotic multi-resistance made more and more stringent the developing of new anti-microbial strategies. The purpose of the present study was to investigate the antimicrobial potential of six (6) newly synthesized chemical compounds (derivating from phenantroline and dimethylguanin-copper complex combinations) versus 97 enterobacterial strains isolated from the hospital environment. The qualitative screening of the antimicrobial activity of the chemical compounds was performed by an adapted diffusion method. The minimal inhibitory concentrations (MIC) of the active chemical compounds were established by Mueller Hinton broth microdillution method. The tested chemical compounds were also tested for their ability to inhibit microbial adherence and biofilm development on inert substrata by a simple microtiter method. All six chemical compounds proved to have antimicrobial activity versus the most of the tested strains, the phenantroline derivatives exhibiting higher antimicrobial activity than the dimethylguanidine-copper complex combinations. The subinhibitory concentrations of the tested chemical products slightly inhibited the adherence ability of the bacterial strains to the inert substratum. Our results demonstrated that phenantroline derivatives may represent a new strategy of antimicrobial treatment, simultaneously with the bactericidal effect, the subinhibitory concentrations of these newly synthesized chemical compounds decreasing the adherence ability of bacteria to the inert substratum.

Malaysian. J. Microbiol, 2008

Forty soil samples of agriculture soil were collected from two different sites in Sohag province,... more Forty soil samples of agriculture soil were collected from two different sites in Sohag province, Egypt, during hot and cold seasons. Twenty samples were from soil irrigated with canal water (site A) and twenty samples were from soil irrigated with wastewater (site B). This study aimed to compare the incidence of plasmids in bacteria isolated from soil and to investigate the occurrence of metal and antibiotic resistance bacteria, and consequently to select the potential application of these bacteria in bioremediation. The total bacterial count (CFU/gm) in site (B) was higher than that in site (A). Moreover, the CFU values in summer were higher than those values in winter at both sites. A total of 771 bacterial isolates were characterized as Bacillus, Micrococcus, Staphylococcus, Pseudomonas, Eschershia, Shigella, Xanthomonas, Acetobacter, Citrobacter, Enterobacter, Moraxella and Methylococcus. Minimum inhibitory concentrations (MICs) of Pb +2 , Cu +2 , Zn +2

Acta Microbiologica Et Immunologica Hungarica, 2009

The dcuSR operon of Escherichia coli encodes a two-component sensor/kinase-response/regulator sys... more The dcuSR operon of Escherichia coli encodes a two-component sensor/kinase-response/regulator system. This system regulates gene expression in response to external C 4 -dicarboxylates. During entry into stationary phase Gram-negative bacteria express genes that impart cellular resistance to environmental stresses. In E. coli , 50 or more genes are triggered by sigma factor ( sigma s ) during entry into stationary phase. Multi-copy dcuS-lacZ and chromosomally integrated dcuS-lacZ fusions analysis showed that the expression of dcuSR is positively regulated during growth phase. Many genes that are required for stationary-phase adaptation are controlled by RpoS, a conserved alternative sigma factor, whose expression is, in turn, controlled by many factors. To understand whether the dcuSR is dependent upon RpoS, a RpoS- dcuS-lacZ strain was generated. beta -Galactosidase assay and Western blot analysis reported that the generated RpoS- dcuS-lacZ strain and the wild type showed the same expression during stationary phase. Surprisingly, the growth phase-dependence of the expression of dcuSR is still present in RpoS- dcuS-lacZ strain suggesting that other growth-phase-dependent regulatory mechanisms (might be the DcuSR system or cAMP/CRP), in addition to RpoS, may control post-exponential dcuSR expression.

As demand for reduction of the use of chemical additives in food and for more natural and microbi... more As demand for reduction of the use of chemical additives in food and for more natural and microbiologically safe food products is increasing, bacteriocins may have considerable potential for food preservation. This work aimed to isolate Lactobacillus strains of potential bioprotective application from Egyptian home-made yogurt. Out of 73 strains of isolated Lactobacillus strains, only four strains of Lactobacillus plantarum (AA110, AA125, AA135 and AA140) demonstrated production of antagonistic activity against foodborne pathogens. The antimicrobial agent excreted by L. plantarum AA135 was the most active against a wide range of Gram-positive and Gram-negative pathogens. Because of the interesting inhibition spectrum of agent AA135, it was selected for further characterization. The activity of the antimicrobial substance produced from L. plantarum AA135 was resistant to heat (121 o C for 30 min), catalase and lysozyme, but was destroyed by papain, trypsin and pepsin. The AA135 compound was produced during growth phase and, when the neutralized and concentrated supernatant was added to a culture of Pseudomonas aeruginosa in logarithmic phase, it produced a rapid decrease in optical density indicative of cell lysis. The AA135 agent could be extracted from the culture supernatant fluids with n-butanol. When 40% ammonium sulphateprecipitated agent was analysed by 10% SDS-PAGE, two peptides with high molecular sizes of ~45 kDa and <45 kDa were seen. L. plantarum AA135 does not contain any plasmid, which indicates that the antagonistic compound' s production is encoded by chromosomal genes. The antibacterial agent was characterized as a bacteriocin-like inhibitory substance and designated as plantaricin AA135. The potential significance for improving the hygiene and safety of the food products is discussed.

Four diazinon-degrading bacteria were isolated from agricultural soil by using an enrichment tech... more Four diazinon-degrading bacteria were isolated from agricultural soil by using an enrichment technique. The biochemical analysis and molecular method including RFLP indicated that these isolates were identical, and one strain designated DI101 was selected for further study. Phylogenetic analysis based on 16S rDNA sequencing indicated that the strain DI101 clearly belongs to the Serratia marcescens group. The ability of the strain to utilize diazinon as a source of carbon and phosphorus was investigated under different culture conditions. The DI101 strain was able to completely degrade 50 mg/l diazinon in MSM within 11 days with a degradation rate of 0.226 day -1 . The inoculation of sterilized soil treated with 100 mg/kg of diazinon with 10 6 CFU/g DI101 resulted in a faster degradation rate than was recorded in non-sterilized soil. The diazinon degradation rate by DI101 was efficient at temperatures from 25 to 30 o C and at pHs from 7.0 to 8.0. The degradation rate of diazinon was not affected by the absence of a phosphorus supplement, and addition of other carbon sources (glucose or succinate) resulted in the slowing down of the degradation rate. The maximum degradation rate (V max ) of diazinon was 0.292 day -1 and its saturation constant (K s ) was 11 mg/l, as determined by a Michaelis-Menten curve. The strain was able to degrade diethylthiophosphate-containing organophosphates such as chlorpyrifos, coumaphos, parathion, and isazofos when provided as a source of carbon and phosphorus, but not ethoprophos, cadusafos, and fenamiphos. These results propose useful information for the potential application of the DI101 strain in bioremediation of pesticide-contaminated environments.

Bacteria capable of degrading the pesticide, cadusafos, were isolated from agricultural soil usin... more Bacteria capable of degrading the pesticide, cadusafos, were isolated from agricultural soil using an enrichment method. In this way, five distinct cadusafosdegrading strains of Pseudomonas putidia were isolated, and were characterized using morphological and biochemical analysis, as well as 16S rRNA sequencing. Strain PC1 exhibited the greatest cadusafos degradation rate and was consequently selected for further investigation. Degradation of cadusafos by strain PC1 was rapid at 20 and 37°C, but was greatly reduced (*1.5-fold) by the presence of carbon sources. Strain PC1 was able to effectively degrade cadusafos in sterilized soil using low inoculum levels. The maximum degradation rate of cadusafos (V max ) was calculated as 1.1 mg l -1 day -1 , and its saturation constant (K s ) was determined as 2.5 mg l -1 . Bacteria such as strain PC1, that use cadusafos as a carbon source, could be employed for the bioremediation of sites contaminated with pesticides.

Twenty-three bacterial isolates from polluted water and soil were screened for heavy metals resis... more Twenty-three bacterial isolates from polluted water and soil were screened for heavy metals resistance (i.e., Al(3+), Co(2+), and Cu(2+)). The most potent isolate was identified by morphological characteristics, biochemical tests and confirmed by API20E kits as Providencia rettgeri MAM-4. Removal of Al(3+) from aqueous solution by P. rettgeri is more efficient (∼fourfold) than that by B. cereus ATCC 11778 (a comparison strain) at concentration of 200 mg L(-1) Al(3+). P. rettgeri was able to remove Co(2+) more than B. cereus ATCC 11778 at concentration of 50 mg L(-1) Co(2+). Inoculation of P. rettgeri into clay enhanced significantly the removal of Al(3+), Co(2+), and Cu(2+). P. rettegri MI (mutant strain) was able to tolerate more Al(3+) than that of the parent strain. P. rettgeri was resistant to 7 out of 15 antibiotics tested. P. rettgeri MAM-4 isolated from wastewater had ability to remove Al(3+), Co(2+), and Cu(2+) efficiently from aqueous media; and enhanced significantly metal biosporption by clay. This study has revealed that P. rettgeri could be employed as an effective and economic technology for the removal such metal elements from polluted environment.

The partial characterization of a bacteriocin produced by a human Lactobacillus delbrueckii isola... more The partial characterization of a bacteriocin produced by a human Lactobacillus delbrueckii isolate with probiotic potential. Methods and Results: A bacterocin, UO004, was partially puri®ed by cation exchange followed by a hydrophobic interaction column, biochemically characterized and the N-terminal region sequenced. Bacteriocin UO004 was found to be a hydrophobic, heat-stable polypeptide with an apparent molecular mass of 6 kDa. It was also stable and active over a wide pH range. Conclusions: The active compound was proteinaceous, heat-stable, and had a bactericidal (and bacteriolytic) mode of action on a limited number of micro-organisms. Such a narrow spectrum of activity is typical for bacteriocins produced by intestinal Lactobacillus. Signi®cance and Impact of the Study: Bacteriocin UO004 from a probiotic strain is a new compound that does not share any homology with any other known lactic acid bacteria bacteriocin. Furthermore, Lact. delbrueckii is regarded as a suitable starter for the production of fermented milks.

The effect of extracts (at 0.5, 1.0, 1.5 & 2.0 mg/ml) of six desert plant species commonly used i... more The effect of extracts (at 0.5, 1.0, 1.5 & 2.0 mg/ml) of six desert plant species commonly used in curing the dermatophytic disease was studied on mycelial growth and protein patterns of three dermatophyte fungi namely; Microsporom gypseum, Microsporum canis and Aspergillus niger. Dermatophyte fungi were isolated from skin and hairs of skin diseased patients. Plant species [Mentha pulegium L., Gnaphalium luteo-album, Adenis microcarpus, Halophyllum tuberculatum (Forssk), Melilotus indicus & Mentha microphylla C. Kock] were collected from New Valley Governorate, Egypt. The occurrence of surface fungi in each plant part used for extract preparation was also studied. Low concentration (0.5 mg/mL) of some plant extracts generally favoured mycelial growth of Microsporum canis and Aspergillus niger. In contrast, drastic inhibition in mycelial growth of Microsporum gypseum and Aspergillus niger was observed at high concentrations (1.5 & 2.0 mg/mL) of all plant extracts. Microsporum canis was less affected by plant extracts than the other two fungi. Plant extracts suppressed the expression of ∼ 120 kDa protein band in Microsporum gypseum and enhanced the ∼ 199 kDa protein band in Microsporum canis. Reduction of protein band in conjunction with the inhibition of mycelial growth suggested that the extracts of the tested plant species seem to contain active fungicidal chemical substances.

Annals of Microbiology, 2011

The aim of this work was to investigate the effect of growth conditions on the maximum activity o... more The aim of this work was to investigate the effect of growth conditions on the maximum activity of bacteriocin production by Lactobacillus acidophilus AA11. The bacteriocin was produced at maximum activity in M17 broth supplemented with 0.5% lactose (M17L). The maximum growth of Lactobacillus acidophilus AA11 was obtained at 37°C, while the optimal temperature for the bacteriocin production was 30°C. The pH of bacterial culture also affected bacteriocin production. The optimal pH for bacterial growth and bacteriocin production was 6.5. Moreover, carbon and nitrogen sources significantly influenced the production of bacteriocin. The bacteriocin yield was at least 4-fold higher in M17 broth supplemented with lactose compared to other carbon sources. The optimal organic nitrogen source for bacteriocin production was yeast extract (4%). The addition of KH2PO4, CaCl2 or NH4PO4 into the medium resulted in significant suppression of bacteriocin; however, incorporation of MnSO4 resulted in an impressive increase in bacteriocin production. No increase in bacteriocin production was recorded in medium supplemented with vitamins. The addition of glycerol to the growth medium decreased bacteriocin production. Consequently, maximum bacteriocin activity was obtained in M17L medium (pH 6.5) supplemented with 4% yeast extract and MnSO4 at 30°C. This optimization of bacteriocin production by modification of environmental growth conditions will greatly benefit efficient commercial application.

Acta Microbiologica Et Immunologica Hungarica, 2007

Malathion is an organophosphate insecticide that has been widely used for both domestic and comme... more Malathion is an organophosphate insecticide that has been widely used for both domestic and commercial agricultural purposes. However, malathion has the potential to produce toxic effects in mammalian systems. In this study, Pseudomonas aeruginosa AA 112 which was isolated from soil using enrichment technique could utilize the malathion as a sole carbon source and a source of energy. Pseudomonas aeruginosa AA112 was able to grow in MSMPY medium containing 42.75 mg/ml malathion. However, the optimum concentration of malathion which supported the maximum bacterial growth was found to be 22. 8 mg/ml. Malathion was used as an initial source of energy and carbon when it was found without additional carbon sources (in MSM medium) while it was utilized as second source of energy and carbon in a nutrient-supplemented medium (in MSMPY medium). Moreover, lead acetate test indicated that malathion was first attacked at a sulphur site 1-2 hours after the start of incubation. TLC and IR analysis indicated that malathion was completely degraded into diethyl succinate, hydrogen sulphide and phosphates. Therefore a malathion degradation pathway was proporsed. The degradation of malathion is attributed to the genes located on the chromosome and at least three proteins of high molecular size might be involved in malathion utilization. Bacteria able to use malathion as a food source or metabolize its residues in the environment to inactive, less toxic, and harmless compounds, could be used in bioremediation of an environmental pollution caused by the pesticide.

Acta Microbiologica Et Immunologica Hungarica, 2007

The production of antimicrobial peptides (AMPs) is a major defense mechanism against pathogen inf... more The production of antimicrobial peptides (AMPs) is a major defense mechanism against pathogen infestation and of particular importance for insects relying exclusively on an innate immune system. Here, we report on the characterization of three AMPs from the carpenter ant Camponotus floridanus. Due to sequence similarities and amino acid composition these peptides can be classified into the cysteine-rich (e.g. defensin) and glycine-rich (e.g. hymenoptaecin) AMP groups, respectively. The gene and cDNA sequences of these AMPs were established and their expression was shown to be induced by microbial challenge. We characterized two different defensin genes. The defensin-2 gene has a single intron, whereas the defensin-1 gene has two introns. The deduced amino acid sequence of the C. floridanus defensins is very similar to other known ant defensins with the exception of a short C-terminal extension of defensin-1. The hymenoptaecin gene has a single intron and a very peculiar domain structure. The corresponding precursor protein consists of a signal-and a pro-sequence followed by a hymenoptaecin-like domain and six directly repeated hymenoptaecin domains. Each of the hymenoptaecin domains is flanked by an EAEP-spacer sequence and a RR-site known to be a proteolytic processing site. Thus, proteolytic processing of the multipeptide precursor may generate several mature AMPs leading to an amplification of the immune response. Bioinformatical analyses revealed the presence of hymenoptaecin genes with similar multipeptide precursor structure in genomes of other ant species suggesting an evolutionary conserved important role of this gene in ant immunity.

Acta Microbiologica Et Immunologica Hungarica, 2008

Water is necessary to life so when supplied as drinking water to consumers, a satisfactory qualit... more Water is necessary to life so when supplied as drinking water to consumers, a satisfactory quality must be maintained. In Egypt, infectious intestinal diseases are the major cause of hospitalization in almost all regions. The purpose of this study was to evaluate the microbiological quality of treated and untreated water samples from urban and rural communities. Thirty-five samples of treated (chlorinated) water from taps, 25 samples of bottled water and 15 samples of hand pump (untreated) water collected from different cities alongside the River Nile during the winter of 2007 were bacteriologically tested for safety as drinking water. This study indicated good quality of tap water and bottled water. The untreated water samples (hand pumps) were, however, slightly contaminated by faecal coliforms, faecal enterococci, Clostridium perfringens, Salmonella and Shigella. Consequently, the consumers in the villages receiving water through hand pumps are often exposed to the risk of water-borne diseases due to inadequate treatment of the raw water. Therefore, there are guidelines necessary to protect groundwater quality. Moreover, PCR-amplified by some functional gene fragments such as dctA, dcuB, frdA, dcuS and dcuR genes of the E. coli was adapted for use as a non-cultivation-based molecular approach for detection of E. coli populations from water samples without the need for pure and identified cultures.

Journal of Bacteriology, 2004

The DcuS-DcuR system of Escherichia coli is a two-component sensor-regulator that controls gene e... more The DcuS-DcuR system of Escherichia coli is a two-component sensor-regulator that controls gene expression in response to external C 4 -dicarboxylates and citrate. The DcuS protein is particularly interesting since it contains two PAS domains, namely a periplasmic C 4 -dicarboxylate-sensing PAS domain (PASp) and a cytosolic PAS domain (PASc) of uncertain function. For a study of the role of the PASc domain, three different fragments of DcuS were overproduced and examined: they were PASc-kinase, PASc, and kinase. The two kinase-domaincontaining fragments were autophosphorylated by [␥-32 P]ATP. The rate was not affected by fumarate or succinate, supporting the role of the PASp domain in C 4 -dicarboxylate sensing. Both of the phosphorylated DcuS constructs were able to rapidly pass their phosphoryl groups to DcuR, and after phosphorylation, DcuR dephosphorylated rapidly. No prosthetic group or significant quantity of metal was found associated with either of the PASc-containing proteins. The DNA-binding specificity of DcuR was studied by use of the pure protein. It was found to be converted from a monomer to a dimer upon acetylphosphate treatment, and native polyacrylamide gel electrophoresis suggested that it can oligomerize. DcuR specifically bound to the promoters of the three known DcuSR-regulated genes (dctA, dcuB, and frdA), with apparent K D s of 6 to 32 M for untreated DcuR and <1 to 2 M for the acetylphosphate-treated form. The binding sites were located by

ROMANIAN ARCHIVES, 1971

The presence of the specific antibodies for some enterobacteria -Yersinia, Salmonella and Shigell... more The presence of the specific antibodies for some enterobacteria -Yersinia, Salmonella and Shigella was investigated in patients hospitalized in the period 2000 -2007 with reactive arthritis and other rheumatoid diseases. The antibacterial antibodies in the diagnosis titres were found in 172 out of 1102 (15.6 %) patients. Increased antibodies levels to Yersinia were detected in the sera from 113 (65.7 %) of the 172 patients, for Shigella in 47 (27.3 %) and for Salmonella in 12 (7.0 %) cases. From all serologically positive patients 126 (73.2 %) had clinical diagnosis of reactive arthritis and 46 (26.7%) other rheumatoid diseases (ankylosing spondilytis, Reiter's syndrome, sacroilitis). The most serologically positive cases (63.9 %) were of middle-age (30-50 years). There were no significant differences between sexes among serologically positive cases. ABSTRACT Growth of Lactobacillus plantarum AA135 in MRS broth at 30 o C yielded maximal plantaricin AA13 activity of 10000 AU/ml at pH 3.8 after 16 hours. Maximal activity (10000 AU/ml) of plantaricin AA13 was recorded in MRS broth at initial pH of 5 or 5.5. Optimal production (10000 AU/ml) was recorded in the presence of tryptone (20 g/l), a combination of tryptone plus meat extract (1:0.6) or tryptone with yeast extract (1:0.6) as sole nitrogen source. Growth of Lactobacillus plantarum AA135 in the presence of 20 g/l glucose yielded bacteriocin activity of 10000 AU/ml. Moreover, when 40 g/l glucose was added, the plantaricin AA13 levels doubled to 20000 AU/ml. Concentrations of 5, 10 and 20 g/l K 2 HPO 4 lowered bacteriocin activity by 60 %. Supplementing MRS with 1 g/l or more glycerol repressed bacteriocin production. Maximal activity of 20000 AU/ml was recorded in MRS supplemented with Vitamin DL-6,8-thioctic acid. ABSTRACT Introduction. The emergence of the bacterial antibiotic multi-resistance made more and more stringent the developing of new anti-microbial strategies. The purpose of the present study was to investigate the antimicrobial potential of six (6) newly synthesized chemical compounds (derivating from phenantroline and dimethylguanin-copper complex combinations) versus 97 enterobacterial strains isolated from the hospital environment. The qualitative screening of the antimicrobial activity of the chemical compounds was performed by an adapted diffusion method. The minimal inhibitory concentrations (MIC) of the active chemical compounds were established by Mueller Hinton broth microdillution method. The tested chemical compounds were also tested for their ability to inhibit microbial adherence and biofilm development on inert substrata by a simple microtiter method. All six chemical compounds proved to have antimicrobial activity versus the most of the tested strains, the phenantroline derivatives exhibiting higher antimicrobial activity than the dimethylguanidine-copper complex combinations. The subinhibitory concentrations of the tested chemical products slightly inhibited the adherence ability of the bacterial strains to the inert substratum. Our results demonstrated that phenantroline derivatives may represent a new strategy of antimicrobial treatment, simultaneously with the bactericidal effect, the subinhibitory concentrations of these newly synthesized chemical compounds decreasing the adherence ability of bacteria to the inert substratum.

Malaysian. J. Microbiol, 2008

Forty soil samples of agriculture soil were collected from two different sites in Sohag province,... more Forty soil samples of agriculture soil were collected from two different sites in Sohag province, Egypt, during hot and cold seasons. Twenty samples were from soil irrigated with canal water (site A) and twenty samples were from soil irrigated with wastewater (site B). This study aimed to compare the incidence of plasmids in bacteria isolated from soil and to investigate the occurrence of metal and antibiotic resistance bacteria, and consequently to select the potential application of these bacteria in bioremediation. The total bacterial count (CFU/gm) in site (B) was higher than that in site (A). Moreover, the CFU values in summer were higher than those values in winter at both sites. A total of 771 bacterial isolates were characterized as Bacillus, Micrococcus, Staphylococcus, Pseudomonas, Eschershia, Shigella, Xanthomonas, Acetobacter, Citrobacter, Enterobacter, Moraxella and Methylococcus. Minimum inhibitory concentrations (MICs) of Pb +2 , Cu +2 , Zn +2

Acta Microbiologica Et Immunologica Hungarica, 2009

The dcuSR operon of Escherichia coli encodes a two-component sensor/kinase-response/regulator sys... more The dcuSR operon of Escherichia coli encodes a two-component sensor/kinase-response/regulator system. This system regulates gene expression in response to external C 4 -dicarboxylates. During entry into stationary phase Gram-negative bacteria express genes that impart cellular resistance to environmental stresses. In E. coli , 50 or more genes are triggered by sigma factor ( sigma s ) during entry into stationary phase. Multi-copy dcuS-lacZ and chromosomally integrated dcuS-lacZ fusions analysis showed that the expression of dcuSR is positively regulated during growth phase. Many genes that are required for stationary-phase adaptation are controlled by RpoS, a conserved alternative sigma factor, whose expression is, in turn, controlled by many factors. To understand whether the dcuSR is dependent upon RpoS, a RpoS- dcuS-lacZ strain was generated. beta -Galactosidase assay and Western blot analysis reported that the generated RpoS- dcuS-lacZ strain and the wild type showed the same expression during stationary phase. Surprisingly, the growth phase-dependence of the expression of dcuSR is still present in RpoS- dcuS-lacZ strain suggesting that other growth-phase-dependent regulatory mechanisms (might be the DcuSR system or cAMP/CRP), in addition to RpoS, may control post-exponential dcuSR expression.

As demand for reduction of the use of chemical additives in food and for more natural and microbi... more As demand for reduction of the use of chemical additives in food and for more natural and microbiologically safe food products is increasing, bacteriocins may have considerable potential for food preservation. This work aimed to isolate Lactobacillus strains of potential bioprotective application from Egyptian home-made yogurt. Out of 73 strains of isolated Lactobacillus strains, only four strains of Lactobacillus plantarum (AA110, AA125, AA135 and AA140) demonstrated production of antagonistic activity against foodborne pathogens. The antimicrobial agent excreted by L. plantarum AA135 was the most active against a wide range of Gram-positive and Gram-negative pathogens. Because of the interesting inhibition spectrum of agent AA135, it was selected for further characterization. The activity of the antimicrobial substance produced from L. plantarum AA135 was resistant to heat (121 o C for 30 min), catalase and lysozyme, but was destroyed by papain, trypsin and pepsin. The AA135 compound was produced during growth phase and, when the neutralized and concentrated supernatant was added to a culture of Pseudomonas aeruginosa in logarithmic phase, it produced a rapid decrease in optical density indicative of cell lysis. The AA135 agent could be extracted from the culture supernatant fluids with n-butanol. When 40% ammonium sulphateprecipitated agent was analysed by 10% SDS-PAGE, two peptides with high molecular sizes of ~45 kDa and <45 kDa were seen. L. plantarum AA135 does not contain any plasmid, which indicates that the antagonistic compound' s production is encoded by chromosomal genes. The antibacterial agent was characterized as a bacteriocin-like inhibitory substance and designated as plantaricin AA135. The potential significance for improving the hygiene and safety of the food products is discussed.

Four diazinon-degrading bacteria were isolated from agricultural soil by using an enrichment tech... more Four diazinon-degrading bacteria were isolated from agricultural soil by using an enrichment technique. The biochemical analysis and molecular method including RFLP indicated that these isolates were identical, and one strain designated DI101 was selected for further study. Phylogenetic analysis based on 16S rDNA sequencing indicated that the strain DI101 clearly belongs to the Serratia marcescens group. The ability of the strain to utilize diazinon as a source of carbon and phosphorus was investigated under different culture conditions. The DI101 strain was able to completely degrade 50 mg/l diazinon in MSM within 11 days with a degradation rate of 0.226 day -1 . The inoculation of sterilized soil treated with 100 mg/kg of diazinon with 10 6 CFU/g DI101 resulted in a faster degradation rate than was recorded in non-sterilized soil. The diazinon degradation rate by DI101 was efficient at temperatures from 25 to 30 o C and at pHs from 7.0 to 8.0. The degradation rate of diazinon was not affected by the absence of a phosphorus supplement, and addition of other carbon sources (glucose or succinate) resulted in the slowing down of the degradation rate. The maximum degradation rate (V max ) of diazinon was 0.292 day -1 and its saturation constant (K s ) was 11 mg/l, as determined by a Michaelis-Menten curve. The strain was able to degrade diethylthiophosphate-containing organophosphates such as chlorpyrifos, coumaphos, parathion, and isazofos when provided as a source of carbon and phosphorus, but not ethoprophos, cadusafos, and fenamiphos. These results propose useful information for the potential application of the DI101 strain in bioremediation of pesticide-contaminated environments.

Bacteria capable of degrading the pesticide, cadusafos, were isolated from agricultural soil usin... more Bacteria capable of degrading the pesticide, cadusafos, were isolated from agricultural soil using an enrichment method. In this way, five distinct cadusafosdegrading strains of Pseudomonas putidia were isolated, and were characterized using morphological and biochemical analysis, as well as 16S rRNA sequencing. Strain PC1 exhibited the greatest cadusafos degradation rate and was consequently selected for further investigation. Degradation of cadusafos by strain PC1 was rapid at 20 and 37°C, but was greatly reduced (*1.5-fold) by the presence of carbon sources. Strain PC1 was able to effectively degrade cadusafos in sterilized soil using low inoculum levels. The maximum degradation rate of cadusafos (V max ) was calculated as 1.1 mg l -1 day -1 , and its saturation constant (K s ) was determined as 2.5 mg l -1 . Bacteria such as strain PC1, that use cadusafos as a carbon source, could be employed for the bioremediation of sites contaminated with pesticides.

Twenty-three bacterial isolates from polluted water and soil were screened for heavy metals resis... more Twenty-three bacterial isolates from polluted water and soil were screened for heavy metals resistance (i.e., Al(3+), Co(2+), and Cu(2+)). The most potent isolate was identified by morphological characteristics, biochemical tests and confirmed by API20E kits as Providencia rettgeri MAM-4. Removal of Al(3+) from aqueous solution by P. rettgeri is more efficient (∼fourfold) than that by B. cereus ATCC 11778 (a comparison strain) at concentration of 200 mg L(-1) Al(3+). P. rettgeri was able to remove Co(2+) more than B. cereus ATCC 11778 at concentration of 50 mg L(-1) Co(2+). Inoculation of P. rettgeri into clay enhanced significantly the removal of Al(3+), Co(2+), and Cu(2+). P. rettegri MI (mutant strain) was able to tolerate more Al(3+) than that of the parent strain. P. rettgeri was resistant to 7 out of 15 antibiotics tested. P. rettgeri MAM-4 isolated from wastewater had ability to remove Al(3+), Co(2+), and Cu(2+) efficiently from aqueous media; and enhanced significantly metal biosporption by clay. This study has revealed that P. rettgeri could be employed as an effective and economic technology for the removal such metal elements from polluted environment.

The partial characterization of a bacteriocin produced by a human Lactobacillus delbrueckii isola... more The partial characterization of a bacteriocin produced by a human Lactobacillus delbrueckii isolate with probiotic potential. Methods and Results: A bacterocin, UO004, was partially puri®ed by cation exchange followed by a hydrophobic interaction column, biochemically characterized and the N-terminal region sequenced. Bacteriocin UO004 was found to be a hydrophobic, heat-stable polypeptide with an apparent molecular mass of 6 kDa. It was also stable and active over a wide pH range. Conclusions: The active compound was proteinaceous, heat-stable, and had a bactericidal (and bacteriolytic) mode of action on a limited number of micro-organisms. Such a narrow spectrum of activity is typical for bacteriocins produced by intestinal Lactobacillus. Signi®cance and Impact of the Study: Bacteriocin UO004 from a probiotic strain is a new compound that does not share any homology with any other known lactic acid bacteria bacteriocin. Furthermore, Lact. delbrueckii is regarded as a suitable starter for the production of fermented milks.

The effect of extracts (at 0.5, 1.0, 1.5 & 2.0 mg/ml) of six desert plant species commonly used i... more The effect of extracts (at 0.5, 1.0, 1.5 & 2.0 mg/ml) of six desert plant species commonly used in curing the dermatophytic disease was studied on mycelial growth and protein patterns of three dermatophyte fungi namely; Microsporom gypseum, Microsporum canis and Aspergillus niger. Dermatophyte fungi were isolated from skin and hairs of skin diseased patients. Plant species [Mentha pulegium L., Gnaphalium luteo-album, Adenis microcarpus, Halophyllum tuberculatum (Forssk), Melilotus indicus & Mentha microphylla C. Kock] were collected from New Valley Governorate, Egypt. The occurrence of surface fungi in each plant part used for extract preparation was also studied. Low concentration (0.5 mg/mL) of some plant extracts generally favoured mycelial growth of Microsporum canis and Aspergillus niger. In contrast, drastic inhibition in mycelial growth of Microsporum gypseum and Aspergillus niger was observed at high concentrations (1.5 & 2.0 mg/mL) of all plant extracts. Microsporum canis was less affected by plant extracts than the other two fungi. Plant extracts suppressed the expression of ∼ 120 kDa protein band in Microsporum gypseum and enhanced the ∼ 199 kDa protein band in Microsporum canis. Reduction of protein band in conjunction with the inhibition of mycelial growth suggested that the extracts of the tested plant species seem to contain active fungicidal chemical substances.

Annals of Microbiology, 2011

The aim of this work was to investigate the effect of growth conditions on the maximum activity o... more The aim of this work was to investigate the effect of growth conditions on the maximum activity of bacteriocin production by Lactobacillus acidophilus AA11. The bacteriocin was produced at maximum activity in M17 broth supplemented with 0.5% lactose (M17L). The maximum growth of Lactobacillus acidophilus AA11 was obtained at 37°C, while the optimal temperature for the bacteriocin production was 30°C. The pH of bacterial culture also affected bacteriocin production. The optimal pH for bacterial growth and bacteriocin production was 6.5. Moreover, carbon and nitrogen sources significantly influenced the production of bacteriocin. The bacteriocin yield was at least 4-fold higher in M17 broth supplemented with lactose compared to other carbon sources. The optimal organic nitrogen source for bacteriocin production was yeast extract (4%). The addition of KH2PO4, CaCl2 or NH4PO4 into the medium resulted in significant suppression of bacteriocin; however, incorporation of MnSO4 resulted in an impressive increase in bacteriocin production. No increase in bacteriocin production was recorded in medium supplemented with vitamins. The addition of glycerol to the growth medium decreased bacteriocin production. Consequently, maximum bacteriocin activity was obtained in M17L medium (pH 6.5) supplemented with 4% yeast extract and MnSO4 at 30°C. This optimization of bacteriocin production by modification of environmental growth conditions will greatly benefit efficient commercial application.

Acta Microbiologica Et Immunologica Hungarica, 2007

Malathion is an organophosphate insecticide that has been widely used for both domestic and comme... more Malathion is an organophosphate insecticide that has been widely used for both domestic and commercial agricultural purposes. However, malathion has the potential to produce toxic effects in mammalian systems. In this study, Pseudomonas aeruginosa AA 112 which was isolated from soil using enrichment technique could utilize the malathion as a sole carbon source and a source of energy. Pseudomonas aeruginosa AA112 was able to grow in MSMPY medium containing 42.75 mg/ml malathion. However, the optimum concentration of malathion which supported the maximum bacterial growth was found to be 22. 8 mg/ml. Malathion was used as an initial source of energy and carbon when it was found without additional carbon sources (in MSM medium) while it was utilized as second source of energy and carbon in a nutrient-supplemented medium (in MSMPY medium). Moreover, lead acetate test indicated that malathion was first attacked at a sulphur site 1-2 hours after the start of incubation. TLC and IR analysis indicated that malathion was completely degraded into diethyl succinate, hydrogen sulphide and phosphates. Therefore a malathion degradation pathway was proporsed. The degradation of malathion is attributed to the genes located on the chromosome and at least three proteins of high molecular size might be involved in malathion utilization. Bacteria able to use malathion as a food source or metabolize its residues in the environment to inactive, less toxic, and harmless compounds, could be used in bioremediation of an environmental pollution caused by the pesticide.

Acta Microbiologica Et Immunologica Hungarica, 2007

The production of antimicrobial peptides (AMPs) is a major defense mechanism against pathogen inf... more The production of antimicrobial peptides (AMPs) is a major defense mechanism against pathogen infestation and of particular importance for insects relying exclusively on an innate immune system. Here, we report on the characterization of three AMPs from the carpenter ant Camponotus floridanus. Due to sequence similarities and amino acid composition these peptides can be classified into the cysteine-rich (e.g. defensin) and glycine-rich (e.g. hymenoptaecin) AMP groups, respectively. The gene and cDNA sequences of these AMPs were established and their expression was shown to be induced by microbial challenge. We characterized two different defensin genes. The defensin-2 gene has a single intron, whereas the defensin-1 gene has two introns. The deduced amino acid sequence of the C. floridanus defensins is very similar to other known ant defensins with the exception of a short C-terminal extension of defensin-1. The hymenoptaecin gene has a single intron and a very peculiar domain structure. The corresponding precursor protein consists of a signal-and a pro-sequence followed by a hymenoptaecin-like domain and six directly repeated hymenoptaecin domains. Each of the hymenoptaecin domains is flanked by an EAEP-spacer sequence and a RR-site known to be a proteolytic processing site. Thus, proteolytic processing of the multipeptide precursor may generate several mature AMPs leading to an amplification of the immune response. Bioinformatical analyses revealed the presence of hymenoptaecin genes with similar multipeptide precursor structure in genomes of other ant species suggesting an evolutionary conserved important role of this gene in ant immunity.

Acta Microbiologica Et Immunologica Hungarica, 2008

Water is necessary to life so when supplied as drinking water to consumers, a satisfactory qualit... more Water is necessary to life so when supplied as drinking water to consumers, a satisfactory quality must be maintained. In Egypt, infectious intestinal diseases are the major cause of hospitalization in almost all regions. The purpose of this study was to evaluate the microbiological quality of treated and untreated water samples from urban and rural communities. Thirty-five samples of treated (chlorinated) water from taps, 25 samples of bottled water and 15 samples of hand pump (untreated) water collected from different cities alongside the River Nile during the winter of 2007 were bacteriologically tested for safety as drinking water. This study indicated good quality of tap water and bottled water. The untreated water samples (hand pumps) were, however, slightly contaminated by faecal coliforms, faecal enterococci, Clostridium perfringens, Salmonella and Shigella. Consequently, the consumers in the villages receiving water through hand pumps are often exposed to the risk of water-borne diseases due to inadequate treatment of the raw water. Therefore, there are guidelines necessary to protect groundwater quality. Moreover, PCR-amplified by some functional gene fragments such as dctA, dcuB, frdA, dcuS and dcuR genes of the E. coli was adapted for use as a non-cultivation-based molecular approach for detection of E. coli populations from water samples without the need for pure and identified cultures.

Journal of Bacteriology, 2004

The DcuS-DcuR system of Escherichia coli is a two-component sensor-regulator that controls gene e... more The DcuS-DcuR system of Escherichia coli is a two-component sensor-regulator that controls gene expression in response to external C 4 -dicarboxylates and citrate. The DcuS protein is particularly interesting since it contains two PAS domains, namely a periplasmic C 4 -dicarboxylate-sensing PAS domain (PASp) and a cytosolic PAS domain (PASc) of uncertain function. For a study of the role of the PASc domain, three different fragments of DcuS were overproduced and examined: they were PASc-kinase, PASc, and kinase. The two kinase-domaincontaining fragments were autophosphorylated by [␥-32 P]ATP. The rate was not affected by fumarate or succinate, supporting the role of the PASp domain in C 4 -dicarboxylate sensing. Both of the phosphorylated DcuS constructs were able to rapidly pass their phosphoryl groups to DcuR, and after phosphorylation, DcuR dephosphorylated rapidly. No prosthetic group or significant quantity of metal was found associated with either of the PASc-containing proteins. The DNA-binding specificity of DcuR was studied by use of the pure protein. It was found to be converted from a monomer to a dimer upon acetylphosphate treatment, and native polyacrylamide gel electrophoresis suggested that it can oligomerize. DcuR specifically bound to the promoters of the three known DcuSR-regulated genes (dctA, dcuB, and frdA), with apparent K D s of 6 to 32 M for untreated DcuR and <1 to 2 M for the acetylphosphate-treated form. The binding sites were located by