Climatic influence on mesophilic Bacillus cereus and psychrotolerant Bacillus weihenstephanensis populations in tropical, temperate and alpine soil (original) (raw)
Related papers
1999
Sequences of the 16S ribosomal DNA (rDNA) from psychrotolerant and mesophilic strains of the Bacillus cereus group revealed signatures which were specific for these two thermal groups of bacteria. Further analysis of the genomic DNA from a wide range of food and soil isolates showed that B. cereus group strains have between 6 and 10 copies of 16S rDNA. Moreover, a number of these environmental strains have both rDNA operons with psychrotolerant signatures and rDNA operons with mesophilic signatures. The ability of these isolates to grow at low temperatures correlates with the prevalence of rDNA operons with psychrotolerant signatures, indicating specific nucleotides within the 16S rRNA to play a role in psychrotolerance.
Journal of …, 1999
Sequences of the 16S ribosomal DNA (rDNA) from psychrotolerant and mesophilic strains of the Bacillus cereus group revealed signatures which were specific for these two thermal groups of bacteria. Further analysis of the genomic DNA from a wide range of food and soil isolates showed that B. cereus group strains have between 6 and 10 copies of 16S rDNA. Moreover, a number of these environmental strains have both rDNA operons with psychrotolerant signatures and rDNA operons with mesophilic signatures. The ability of these isolates to grow at low temperatures correlates with the prevalence of rDNA operons with psychrotolerant signatures, indicating specific nucleotides within the 16S rRNA to play a role in psychrotolerance.
1998
Detection of psychrotrophic strains (those able to grow at or below 7°C) of the Bacillus cereus group (Bacillus cereus, Bacillus thuringiensis, and Bacillus mycoides) in food products is at present extremely slow with conventional microbiology. This is due to an inability to discriminate these cold-adapted strains from their mesophilic counterparts (those able to grow only above 7°C) by means other than growth at low temperature, which takes 5 to 10 days for detection. Here we report the development of a single PCR assay that, using major cold shock protein-specific primers and appropriate annealing temperatures, is capable of both rapidly identifying bacteria of the B. cereus group and discriminating between psychrotrophic and mesophilic strains. It is intended that this development help to more accurately predict the shelf life of refrigerated pasteurized food and dairy products and to reduce the incidence of food poisoning by psychrotrophic strains of the B. cereus group.
Measurement of soil bacterial colony temperatures and isolation of a high heat-producing bacterium
BMC Microbiology, 2013
Background: The cellular temperatures of microorganisms are considered to be the same as those of their surroundings because the cellular volume is too small to maintain a cellular temperature that is different from the ambient temperature. However, by forming a colony or a biofilm, microorganisms may be able to maintain a cellular temperature that is different from the ambient temperature. In this study, we measured the temperatures of bacterial colonies isolated from soils using an infrared imager and investigated the thermogenesis by a bacterium that increases its colony temperature. Results: The temperatures of some colonies were higher or lower than that of the surrounding medium. A bacterial isolate with the highest colony temperature was identified as Pseudomonas putida. This bacterial isolate had an increased colony temperature when it grew at a temperature suboptimal for its growth. Measurements of heat production using a microcalorimeter showed that the temperature of this extraordinary, microcalorimetrically determined thermogenesis corresponded with the thermographically observed increase in bacterial colony temperature. When investigating the effects of the energy source on this thermal behavior, we found that heat production by this bacterium increased without additional biomass production at a temperature suboptimal for its growth. Conclusions: We found that heat production by bacteria affected the bacterial colony temperature and that a bacterium identified as Pseudomonas putida could maintain a cellular temperature different from the ambient temperature, particularly at a sub-optimal growth temperature. The bacterial isolate P. putida KT1401 increased its colony temperature by an energy-spilling reaction when the incubation temperature limited its growth.
Thermal disruption of soil bacterial assemblages decreases diversity and assemblage similarity
Ecosphere
The metabolic theory of ecology assumes that rates of selection and adaptation for organisms are functions of temperature. Niche theory predicts that strong selection pressure should simplify assemblages as species are extirpated and taxa pre-adapted for the new environment thrive. Here, we use closed mesocosms to test the prediction that higher temperatures decrease species richness and increase assemblage similarity more and faster than lower temperatures. We incubated two temperate forest soil types at constant temperatures from 10°to 35°, destructively sampling mesocosms at 30, 180, and 440 d. We quantified taxonomic richness and assemblage similarity of soil bacteria using 16S rRNA gene amplicons. As predicted, mesocosms at higher temperatures lost more taxa than those at lower temperature. Contrary to predictions, the simplified assemblages at higher temperatures became less similar to each other over time. After 440 d of incubation, the number of taxa lost was a linear function of the difference between treatment temperature and site mean annual temperature, while assemblage similarity decreased as an accelerating function of this temperature difference.
Journal of Microbiological Methods, 1998
The paper describes a novel PCR assay for discriminating psychrotolerant and mesophilic strains of the Bacillus cereus group by targeting of 16S rDNA signatures. Application of the assay circumvents long-term growth tests at low temperature currently used to detect psychrotolerant strains. PCR was performed with pure cultures. A 100% correlation of PCR and growth data at 78C was obtained for the 194 B. cereus group strains tested. Potential applications of the assay for the dairy industry and agriculture are suggested.
2014
To study culturable bacterial diversity under subzero temperature conditions and their possible functional annotation, soil and water samples from Leh Ladakh region were analysed. Ten different nutrient combinations were used to isolate the maximum possible culturable morphotypes. A total of 325 bacterial isolates were characterized employing 16S rDNA-Amplified Ribosomal DNA Restriction Analysis with three restriction endonucleases AluI, MspI and HaeIII, which led to formation of 23–40 groups for the different sites at 75 % similarity index, adding up to 175 groups. Phylogenetic analysis based on 16S rRNA gene sequencing led to the identification of 175 bacteria, grouped in four phyla, Firmicutes (54 %), Proteobacteria (28 %), Actinobacteria (16 %) and Bacteroidetes (3 %), and included 29 different genera with 57 distinct species. Overall 39 % of the total morphotypes belonged to the Bacillus and Bacillus derived genera (BBDG) followed by Pseudomonas (14 %), Arthrobacter (9 %), Exiguobacterium (8 %), Alishewanella (4 %), Brachybacterium, Providencia, Planococcus (3 %), Janthinobacterium, Sphingobacterium, Kocuria (2 %) and Aurantimonas, Citricoccus, Cellulosimicrobium, Brevundimonas, Desemzia, Flavobacterium, Klebsiella, Paracoccus, Psychrobacter, Sporosarcina, Staphylococcus, Sinobaca, Stenotrophomonas, Sanguibacter, Vibrio (1 %). The representative isolates from each cluster were screened for their plant growth promoting characteristics at low temperature (5–15 C). Variations were observed among strains for production of ammonia, hydrogen cyanide, indole-3-acetic acid and siderophore, solubilisation of phosphate, 1-aminocyclopropane-1-carboxylate deaminase activity and biocontrol activity against Rhizoctonia solani and Macrophomina phaseolina. Cold adapted microbes may have application as inoculants and biocontrol agents in crops growing at high altitudes under cold climate condition.
SN Applied Sciences
The Himalayan Mountains are placed among the globally recognized biodiversity hot spots. While the Indian Himalayan Region (IHR) has been subjected to extensive studies on plant and animal biodiversity, microbial diversity is now being studied for its bioprospection. The present paper deals with the evaluation of bacterial diversity in high-altitude soil samples from IHR following polyphasic approach including comparison between the MALDI-TOF mass spectrometry and 16S rRNA gene sequencing for species-level identification. Initially, a culture collection of large number of bacterial isolates was established in the laboratory. Performing morphological and biochemical screenings, sixty-one representative isolates were selected for mass spectrometry and gene sequencing. Both the methods emerged with bacterial identification showing maximum number of Bacillus followed by Pseudomonas species. The other frequently isolated strains belonged to the genera Alcaligenes, Carnobacterium, Lysinibacillus, Microbacterium, Paenarthrobacter, Rhodococcus, Serratia and Stenotrophomonas. Although the MALDI-TOF technique appeared to be advantageous as less time-consuming in comparison with 16S rRNA-based method, the discrepancies at species level indicated the limited database of MALDI Biotyper and species complexity in the genera. The remarkable characteristics of the bacterial isolates were their tolerance to wide range of pH and temperature. Their potential to produce industrially valuable enzymes indicated their importance in bioprospection. Accessioning of these bacterial isolates in microbial culture collections is a cautious effort for their availability to conduct advanced research on these cold-adapted bacteria in future.
Bacillus weihenstephanensis sp. nov. is a new psychrotolerant species of the Bacillus cereus group
International …, 1998
The Bacillus cereus group comprises the four valid species Bacillus cereus, Bacillus mycoides, Bacillus fhuringiensis and Bacillus anthracis. Some isolates of B. cereus are known to be psychrotolerant (growth a t 7 O C or below). Here, specific sequence differences are described between the 165 rDNA, the 235 rDNA, the 165-235 rDNA spacer region and the genes of the major cold-shock protein homologue cspA in a variety of psychrotolerant and mesophilic B. cereus and B. mycoides strains. Randomly amplified polymorphic DNA analysis using three different primers clearly separated psychrotolerant strains of both species from the rest of the B. cereus group, as did inverse PCR patterns of the rDNA operons. These data strongly support a hitherto unrecognized fifth sub-group within the B. cereus species group comprising psychrotolerant, but not mesophilic, B. cereus strains. Despite the latter finding, the DNA sequences investigated exhibited a high degree of sequence similarity indicating a close relationship between the species of the B. cereus group. Considering the unusual importance of B. cereus in both food poisoning and food spoilage and to avoid merging all species of the group, a new species, Bacillus weihenstephanensis sp. nov., comprising psychrotolerant 'cereus' strains, is proposed. Isolates of the new species grow a t 4-7 "C but not a t 43 OC and can be identified rapidly using rDNA or cspA targeted PCR. The type strain is B. weihenstephanensis WSBC 10204T (= DSM 1182IT).