Psychrotolerant methanogenic archaea:Diversity and cold adaptation mechanisms

Because of their diversity and abundance in a wide range of environments, particularly in cold regions, cold-adaptive archaea are expected to play a pivotal role in material recycling in cold environments. Methanogenic archaea are ubiquitous on earth and produce a large amount of methane （CH4） as their main carbon metabolite. Methanogens are the most laboratory amenda- ble archaea. The few psychrophilic archaea that have been cultured to date are mainly affiliated with methanogens, thus make them a good model for investigating mechanisms of archaeal cold adaptation. Studies of psychrotolerant methanogens have been ongoing since the 1990s. Using Methanocoecoides burtonii, a methanogen isolated from Ace Lake in Antarctica, exten- sive studies on the genomic characteristics associated with cold adaptation have been carried out by the Cavicchioli laboratory. We recently analyzed the genome of another psychrophilic methanogen and identified the gene repertoire associated with cold adaptation. This review summarizes recent studies of psychroactive methanogens, particularly their diversity, the genomics and proteomics associated with their cold adaptation, and the cellular components and proteins likely involved in their cold protec- tion.

Occurrence and Diversity of Marine Yeasts in Antarctica Environments

A total of 28 yeast strains were obtained from the sea sediment of Antarctica.According to the results of routine identi-fication and molecular characterization,the strains belonged to species of Yarrowia lipolytica,Debaryomyces hansenii,Rhodotorula slooffiae,Rhodotorula mucilaginosa,Sporidiobolus salmonicolor,Aureobasidium pullulans,Mrakia frigida and Guehomyces pullu-lans,respectively.The Antarctica yeasts have wide potential applications in biotechnology,for some of them can produce b-galactosidase and killer toxins.

Impacts of Bioinoculants Pseudomonas jesenii MP1 and Rhodococcus qingshengii S10107 on Chickpea (Cicer arietinum L.) Yield and Soil Nitrogen Status

Cold-adapted bioinoculants are considered as harbingers of sustainable hill agriculture. Therefore, two previously characterized psychrotolerant diazotrophs, Pseudomonas jesenii MP1 and Rhodococcus qingshengii S10107, were evaluated for their plant growthpromoting potential for chickpea (Cicer arietinum L.) grown under natural field conditions. Comparative analysis of agronomical and biochemical crop parameters revealed the irrelevance of chemical fertilizers for chickpea production;the diazotrophs alone were sufficient to fulfil the crop's nutritional requirement. However, the integrated use of bacterial strains in combination with urea at 20 kg N ha^-1 as urea was being recommended for higher crop yield and better soil nitrogen status. Quantitative polymerase chain reaction (qPCR) and denaturing gradient gel electrophoresis (DGGE)-based soil bacterial dynamics unveiled the persistence of both diazotrophs until the end of the crop maturation period without affecting the native micro-flora. Therefore, these bioinoculants can be explored as natural nitrogen resource, and an additional incentive in their bio-formulation will be a step towards agricultural sustainability.

Rhodotorula mucilaginosa BPT1 can form arthrospore in response to cold-temperature

Objective:To study carbon and nitrogen utilization pattern and arthrospore formation in a psychrotolerant yeast isolate Rhodotorula mucilaginosa(R.mucilaginosa)BPT1.Methods:Growth of the yeast on minimal synthetic medium supplemented with various carbon and nitrogen compounds as sole carbon or nitrogen source has been studied.Various physico-chemical parameters such as pH,restricted oxygen supply,temperatures,media composition and presence of methionine were tested to examine their effect on arthrospore formation by this known opportunistic pathogen.Results:The psychrotolerant isolate BPT1 identified on the basis of D1/D2 domain of large rDNA sequence characteristics as R.mucilaginosa showed some deviation in carbon and nitrogen utilization patterns from those of other strains of R.mucilaginosa in the CBS data base.Intriguingly,the isolate produced sub-surface hyphal rays around its colony at lower temperatures(4℃and 20℃)on PDA medium;the ray was found to be linearly arranged arthrospores.The arthrospore was not produced in liquid medium,or in presence of methionine or under micro-aerobic condition or at higher temperature.Conclusions:The investigation showed a novel feature i.e.arthrospore was formed by this yeast isolate under specific set of conditions.The results reiterated that only physiological and morphological characteristics were not sufficient to identify a yeast.The ability of R.mucilaginosa to form arthrospores seems to be an adaptive feature in response to extreme environmental condition,and represents adaptive ability having something to do with its ubiquity.