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Phenotypic plasticity in Bacillus cereus strains isolated from various Antarctic habitats

Advances in Polar Science 2013年第4期24卷 213-222页

作者： Rupesh Kumar Sinha kottekkatu padinchati krishnan Cryobiology Laboratory National Centre for Antarctic and Ocean Research

We studied five strains of psychrotolerant Bacillus cereus （B. cereus） isolated from Antarctic snow （BCsn）, ice （BCic）, lake water （BCwt）, sediment （BCsd）, and soil （BCsl） samples in terms of their growth, biochemical properties, and heat shock re- sponses. Analyses of growth kinetics at 4℃ showed that BCsn had the fastest generation time （16.1 h）, whereas BCWT had the slowest （30.8 h）. Strain BCsd formed the largest zone of lipid hydrolysis （18 mm） whereas BCsn formed the smallest zone （3 mm）.Only BCsd produced gelatinase. These physiological differences illustrate adaptations of B. cereus isolates to different niches. Strains BCsl and BCwr were resistant to all 12 of the antibiotics tested. Strains BCsn, BCio, and BCsd were resistant to cell wall synthesis inhibitors （penicillin and ampicillin） and susceptible to protein synthesis inhibitors （tetracycline and streptomycin）. A carbon-substrate utilization assay revealed that BCsn, BCic and BCwr could specifically utilize D-glucose-6-phosphate, salicin, and 2＇-deoxyadenosine, respectively, indicating a degree of metabolic diversity among these Antarctic B. cereus strains. An analy- sis of heat shock proteins （HSPs） produced in response to a 60℃ heat treatment revealed significant variations in the amounts of HSP33 （p = 0.01, df= 4）, HSP44 （p = 0.003, dr= 4）, and HSP60 （p = 0.04, df= 4） among the strains. This emphasizes the impor- tance of HSPs in bacterial taxonomy. These results show that there are considerable adaptive variations among B. cereus strains from extremophilie environments. This could be significant in evaluating the taxonomy and evolution of this species.

关键词： Bacillus cereus Antarctica phenotype heat shock protein carbon utilization

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A characteristic study of humic acids isolated from Arctic fjord sediments

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Advances in Polar Science 2019年第1期30卷 24-34页

作者： Jennees MATHEW Aswathy SHAJI Anu GOPINATH Kottekkattu padinchati krishnan Sanil Vadakkan LOUIS Anoop Pullarkkat PRADEEP School of Ocean Science and Technology Kerala University of Fisheries and Ocean Studies National Centre for Antarctic and Ocean Studies Department of Chemistry St.Albert's College

Humic substances are ubiquitous natural materials found in sediments as a product of biochemical transformation reactions representing a significant proportion of organic carbon cycle on earth. This study involves the analysis of humic substances with special emphasis on humic acids(HAs) in sediments collected from the Kongsfjorden System of Arctic region in June, 2017. The characterization of the isolated HAs were done using various spectroscopic techniques viz. UV-visible, Fluorescence, FTIR and NMR. Isolated HAs were also undergone for elemental analysis along with other characterization. The UV spectral analysis results with a lower E4/E6 ratio suggesting the presence of HAs with high degree of aromaticity and condensation. Indications for the presence of hydroxyl, methyl, methylene, carbonyl, carboxyl, phenol, alcohol and amide groups were obtained from the FTIR spectrums of HAs. NMR spectral characteristics also confirm the presence of OH group as well as the presence of CH protons adjacent to C=X, were X can be any electronegative element. This also confirms the presence of carbonyl group which is also evident in the FTIR spectral studies. Presence of aliphatic regions slightly more dominated with long chain and/or alicyclic moieties rather than methyl groups was also inferred from the results of NMR.

关键词： Kongsfjorden sediments humic acids

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