The present investigation is the first of its kind which aims to study the characteristics of microbial consortium inhabiting one of the natural high background radiation areas of the world, Chavara Coast in Kerala, India. The composition of the microbial community and their structural changes were evaluated under the natural circumstances with exorbitant presence of radionuclides in the sediments and after the radionuclide's recession due to mining effects. For this purpose, the concentration of radionuclides, heavy metals, net radioactivity estimation via gross alpha and beta emitters and other physiochemical characteristics were assessed in the sediments throughout the estuarine stretch. According to the results, the radionuclides had a significant effect in shaping the community structure and composition, as confirmed by the bacterial heterogeneity achieved between the samples. The results indicate that high radioactivity in the background environment reduced the abundance and growth of normal microbial fauna and favoured only the growth of certain extremophiles belonging to families of Piscirickettsiacea, Rhodobacteriacea and Thermodesulfovibrionaceae, which were able to tolerate and adapt towards the ionizing radiation present in the environment. In contrast, communities from Comamondacea, Sphingomonadacea, Moraxellacea and Erythrobacteracea were present in the sediments collected from industrial outlet, reinforcing the potent role of radionuclides in governing the community pattern of microbes present in the natural environment. The study confirms the presence of these novel and unidentified bacterial communities and further opens the possibility of utilizing their usefulness in future prospects.
An effective biosurfactant producer and extremophiles bacteria, Bacillus cereus KH1, was isolated from textile effluent and the biosurfactant was produced using molasses as the sole carbon source. Growth parameters such as pH, temperature, salinity and concentration of molasses were optimised for decolourising the textile effluent with 24-h incubation. The biosurfactant property of B. cereus KH1 was evaluated based on haemolytic activity, oil displacement technique, drop-collapsing test and emulsification index. The results of the produced biosurfactant showed a positive reaction in haemolytic activity, oil displacement technique, drop-collapsing test and exhibiting a 67% emulsification index. The cell-free broth was stable in 40 °C pH 7, 7% salinity and 7% molasses. Thin-Layer Chromatography and Fourier Transform Infrared Spectroscopy analysis revealed that the biosurfactant was a lipopeptide with a yield 2.98 g L-1. These findings proved the synergistic action of B. cereus KH1 with lipopeptide biosurfactant may accelerated the decolourisation efficiency to 87%.
During low-temperature exposure, temperate plant species increase their freezing tolerance in a process termed cold acclimation. The molecular mechanisms involved in cold acclimation have been mostly investigated in Arabidopsis thaliana. In addition, other Brassicaceae species related to A. thaliana have been employed in recent years to study plant stress responses on a phylogenetically broader basis and in some cases with extremophile species with a much higher stress tolerance. In this paper, we briefly summarize cold acclimation responses in A. thaliana and current knowledge about cold acclimation in A. thaliana relatives with special emphasis on Eutrema salsugineum and two closely related Thellungiella species. We then present a transcriptomic and metabolomic analysis of cold acclimation in five A. thaliana and two E. salsugineum accessions that differ widely in their freezing tolerance. Differences in the cold responses of the two species are discussed.
Halophiles are extremophilic microorganisms that grow optimally at high salt concentrations by producing a myriad of equally halotolerant enzymes. Structural haloadaptation of these enzymes adept to thriving under high-salt environments, though are not fully understood. Herein, the study attempts an in silico investigation to identify and comprehend the evolutionary structural adaptation of a halotolerant dehalogenase, DehHX (GenBank accession number: KR297065) of the halotolerant Pseudomonas halophila, over its non-halotolerant counterpart, DehMX1 (GenBank accession number KY129692) produced by Pseudomonas aeruginosa. GC content of the halotolerant DehHX DNA sequence was distinctively higher (58.9%) than the non-halotolerant dehalogenases (55% average GC). Its acidic residues, Asp and Glu were 8.27% and 12.06%, respectively, compared to an average 5.5% Asp and 7% Glu, in the latter; but lower contents of basic and hydrophobic residues in the DehHX. The secondary structure of DehHX interestingly revealed a lower incidence of α-helix forming regions (29%) and a higher percentage of coils (57%), compared to 49% and 29% in the non-halotolerant homologues, respectively. Simulation models showed the DehHX is stable under a highly saline environment (25% w/v) by adopting a highly negative-charged surface with a concomitant weakly interacting hydrophobic core. The study thus, established that a halotolerant dehalogenase undergoes notable evolutionary structural changes related to GC content over its non-halotolerant counterpart, in order to adapt and thrive under highly saline environments.Communicated by Ramaswamy H. Sarma.
Lichen is a symbiotic organism that exists as a single composite body consisting of a mycobiont (fungus) and a photobiont (algae or a cyanobacterium). Many lichen species are considered as extremophiles due to their tolerance to radiation, desiccation, temperature and pollution. However, not all lichen species are tolerant to harsh environmental conditions as several species are sensitive for example to nitrogen, sulphur, acidity, heavy metals, halogens (e.g. fluoride) and ozone. Thus, to better understand why some lichens can withstand exposure to pollutants as opposed to those that are susceptible, we focused on the lichen species of Dirinaria known for their wide distribution in the tropics, subtropics and pantropical, and moderate tolerance to air pollution. Their moderate tolerance to air pollution affords them to thrive in good air quality environments as well as polluted air environments. Lichen samples of Dirinaria sp., UKM-J1 and UKM-K1, were respectively collected from two areas with different levels of air quality based on Air Pollutant Index or API (with index pollutant criteria of PM10, carbon monoxide, ozone, nitrogen dioxide and sulfur dioxide) in the outskirt of Jerantut (UKM-J1), a rural area in the middle of Peninsular Malaysia and the township of Klang (UKM-K1), in a busy area of the Klang Valley, Malaysia. API was monitored throughout 2012-2013 whereby the sample collection site in Klang showed markedly higher concentrations of pollutants in all the index pollutant criteria as compared to that of Jerantut. We performed transcriptome sequencing using Illumina RNA-seq technology and de novo assembly of the transcripts from the lichen samples. Raw reads from both libraries were deposited in the NCBI database with the accession number SRP138994.