Contribution of YthA, a PspC family transcriptional regulator to Lactococcus lactis F44 acid tolerance and nisin yield: a transcriptomic approach (original) (raw)
Related papers
2005
The organic acid lactate is the predominant fermentation product of Lactobacillus plantarum. The undissociated form of this organic acid is a strong growth inhibitor for the organism. Different theories have been postulated to explain the inhibitory effects of lactic acid: (i) toxicity arising from the dissipation of the membrane potential, (ii) acidification of the cytosol, or (iii) intracellular anion accumulation. In general, organic acid stresses are complex to study, since their toxicity is highly dependent on their degree of dissociation and thus on the pH. In this study, transcription profiles of L. plantarum grown in steady-state cultures that varied in lactate/lactic acid concentration, pH, osmolarity and absolute and relative growth rate, were compared by microarray analysis. By doing so, the differential expression of multiple groups of genes could specifically be attributed to the different aspects of lactic acid stress. A highly coherent group of lactic acid-responsive, cell surface protein-encoding genes was identified, to which no function has previously been assigned. Moreover, a group of genes that showed increased expression in response to the combination of lactic acid and a lower growth rate is expected to be involved in the formation of the alternative fermentation end-products malate, acetate and ethanol. One of these pathways is the phosphoketolase bypass that is typical for bifidobacteria.
Gene Expression Analysis of Corynebacterium glutamicum Subjected to Long-Term Lactic Acid Adaptation
Journal of Bacteriology, 2007
Corynebacteria form an important part of the red smear cheese microbial surface consortium. To gain a better understanding of molecular adaptation due to low pH induced by lactose fermentation, the global gene expression profile of Corynebacterium glutamicum adapted to pH 5.7 with lactic acid under continuous growth in a chemostat was characterized by DNA microarray analysis. Expression of a total of 116 genes was increased and that of 90 genes was decreased compared to pH 7.5 without lactic acid, representing 7% of the genes in the genome. The up-regulated genes encode mainly transcriptional regulators, proteins responsible for export, import, and metabolism, and several proteins of unknown function. As much as 45% of the up-regulated open reading frames code for hypothetical proteins. These results were validated using real-time reverse transcription-PCR. To characterize the functions of 38 up-regulated genes, 36 single-crossover disruption mutants were generated and analyzed for their lactic acid sensitivities. However, only a sigB knockout mutant showed a highly significant negative effect on growth at low pH, suggesting a function in organic-acid adaptation. A sigE mutant already displayed growth retardation at neutral pH but grew better at acidic pH than the sigB mutant. The lack of acid-sensitive phenotypes in 34 out of 36 disrupted genes suggests either a considerable redundancy in acid adaptation response or coincidental effects. Other up-regulated genes included genes for ion transporters and metabolic pathways, including carbohydrate and respiratory metabolism. The enhanced expression of the nrd (ribonucleotide reductase) operon and a DNA ATPase repair protein implies a cellular response to combat acid-induced DNA damage. Surprisingly, multiple iron uptake systems (totaling 15% of the genes induced >2-fold) were induced at low pH. This induction was shown to be coincidental and could be attributed to iron-sequestering effects in complex media at low pH.
The acid-stress response in Lactobacillus sanfranciscensis CB1
2001
Lactobacillus sanfranciscensis CB1, an important sourdough lactic acid bacterium, can withstand low pH after initial exposure to sublethal acidic conditions. The sensitivity to low pH varied according to the type of acid used. Treatment of Lb. sanfranciscensis CB1 with chloramphenicol during acid adaptation almost completely eliminated the protective effect, suggesting that induction of protein synthesis was required for the acid-tolerance response. Two constitutively acid-tolerant mutants, CB1-5R and CB1-7R, were isolated using natural selection techniques after sequential exposure to lactic acid (pH 32). Two-dimensional gel electrophoresis analysis of protein expression by non-adapted, acid-adapted and acid-tolerant mutant cells of Lb. sanfranciscensis showed changes in the levels of 63 proteins. While some of the modifications were common to the acid-adapted and acid-tolerant mutant cells, several differences, especially regarding the induced proteins, were determined. The two mutants showed a very similar level of protein expression. Antibodies were used to identify heat-shock proteins DnaJ, DnaK,
Physiological and Metabolic Responses of Functional Lactic Acid Bacteria to Stress Factors
2018
In our study, six functional lactic acid bacterium strains (able to produce bacteriocins, exopolysaccharides, or S-layer proteins) were subjected to different stress conditions in order to evaluate their capacity to adapt to harsh environments. They were cultivated at different temperatures, below and above their optimal growth temperatures. Moreover, they were grown in presence of bile salts or NaCl, or in acidic media. Total proteins, lactic acid production, enzymatic activities and synthesis of the metabolites of biotechnological interest were evaluated for all growth conditions. Over expression of some proteins was detected in the electrophoretic pattern of the total protein extracts from the stressed cultures compared to the control cultures. Enzymatic activities and lactic acid production were, in general, directly related with growth. The tested strains maintained their capacity to synthesize the assayed metabolites under almost all stress conditions. Bacteriocin production o...
Journal of Bacteriology, 2001
The ability of Escherichia coli to survive at low pH is strongly affected by environmental factors, such as composition of the growth medium and growth phase. Exposure to short-chain fatty acids, such as acetate, proprionate, and butyrate, at neutral or nearly neutral pH has also been shown to increase acid survival of E. coli and Salmonella enterica serovar Typhimurium. To investigate the basis for acetate-induced acid tolerance in E. coli O157:H7, genes whose expression was altered by exposure to acetate were identified using gene arrays. The expression of 60 genes was reduced by at least twofold; of these, 48 encode components of the transcriptiontranslation machinery. Expression of 26 genes increased twofold or greater following treatment with acetate. This included six genes whose products are known to be important for survival at low pH. Five of these genes, as well as six other acetate-induced genes, are members of the E. coli RpoS regulon. RpoS, the stress sigma factor, is known to be required for acid tolerance induced by growth at nonlethal low pH or by entry into stationary phase. Disruption of the rpoS gene by a transposon insertion mutation also prevented acetateinduced acid tolerance. However, induction of RpoS expression did not appear to be sufficient to activate the acid tolerance response. Treatment with either NaCl or sodium acetate (pH 7.0) increased expression of an rpoS::lacZ fusion protein, but only treatment with acetate increased acid survival.
Antonie van Leeuwenhoek, 1996
It is now generally recognized that cell growth conditions in nature are often suboptimal compared to controlled conditions provided in the laboratory. Natural stresses like starvation and acidity are generated by cell growth itself. Other stresses like temperature or osmotic shock, or oxygen, are imposed by the environment. It is now clear that defense mechanisms to withstand different stresses must be present in all organisms. The exploration of stress responses in lactic acid bacteria has just begun. Several stress response genes have been revealed through homologies with known genes in other organisms. While stress response genes appear to be highly conserved, however, their regulation may not be. Thus, search of the regulation of stress response in lactic acid bacteria may reveal new regulatory circuits. The first part of this report addresses the available information on stress response in Lactococcus lactis.
Strain-Dependent Transcriptome Signatures for Robustness in Lactococcus lactis
PLOS ONE, 2016
Owing to their spoilage-preventing, texture-improving and flavor-enhancing properties, lactic acid bacteria have a long history of application in food fermentations . One of the most widely used lactic acid bacteria in the food industry is Lactococcus lactis, notably for the production of cheese and butter(milk) . These milk fermentation processes are typically initiated with the addition of starter cultures containing high concentrations of one or multiple L. lactis strains. During the production of these starter cultures prior to application in the food industry, L. lactis strains encounter severe stresses, for example heat and oxidative stress during spray drying . Although spray drying is a cost-effective and energy-efficient method for the preservation of starter cultures, it generally results in a relatively large decrease in viability as compared with other preservation methods such as freezing and freeze drying . Viability of starter cultures is essential for an adequate contribution to the fermentation endproduct, justifying the industrial interest to better understand and improve robustness .
FEMS Microbiology Letters, 2014
Survival of Escherichia coli in food depends on its ability to adapt against encountered stress typically involving induction of stress response genes. In this study, the transcriptional induction of selected acid (cadA, speF) and salt (kdpA, proP, proW, otsA, betA) stress response genes was investigated among five E. coli strains, including three Shiga toxin-producing strains, exposed to sodium chloride or lactic acid stress. Transcriptional induction upon lactic acid stress exposure was similar in all but one E. coli strain, which lacked the lysine decarboxylase gene cadA. In response to sodium chloride stress exposure, proW and otsA were similarly induced, while significant differences were observed between the E. coli strains in induction of kdpA, proP and betA. The kdpA and betA genes were significantly induced in four and three strains, respectively, whereas one strain did not induce these genes. The proP gene was only induced in two E. coli strains. Interestingly, transcriptional induction differences in response to sodium chloride stress exposure were associated with survival phenotypes observed for the E. coli strains in cheese as the E. coli strain lacking significant induction in three salt stress response genes investigated also survived poorly compared to the other E. coli strains in cheese.
Applied and Environmental Microbiology, 2004
This report describes the use of an oligonucleotide macroarray to profile the expression of 375 genes in Lactococcus lactis subsp. lactis IL1403 during heat, acid, and osmotic stress. A set of known stress-associated genes in IL1403 was used as the internal control on the array. Every stress response was accurately detected using the macroarray, compared to data from previous reports. As a group, the expression patterns of the investigated metabolic genes were significantly altered by heat, acid, and osmotic stresses. Specifically, 13 to 18% of the investigated genes were differentially expressed in each of the environmental stress treatments. Interestingly, the methionine biosynthesis pathway genes (metA-metB1 and metB2-cysK) were induced during heat shock, but methionine utilization genes, such as metK, were induced during acid stress. These data provide a possible explanation for the differences between acid tolerance mechanisms of L. lactis strains IL1403 and MG1363 reported previously. Several groups of transcriptional responses were common among the stress treatments, such as repression of peptide transporter genes, including the opt operon (also known as dpp) and dtpT. Reduction of peptide transport due to environmental stress will have important implications in the cheese ripening process. Although stress responses in lactococci were extensively studied during the last decade, additional information about this bacterium was gained from the use of this metabolic array.