Untangling the adaptive strategies of thermophilic bacterium Anoxybacillus rupiensis TPH1 under low temperature.

The present study investigates the low temperature tolerance strategies of thermophilic bacterium Anoxybacillus rupiensis TPH1, which grows optimally at 55 °C , by subjecting it to a temperature down-shift of 10 °C (45 °C) for 4 and 6 h followed by studying its growth, morphophysiological, molecular and proteomic responses. Results suggested that although TPH1 experienced increased growth inhibition, ROS production, protein oxidation and membrane disruption after 4 h of incubation at 45 °C yet maintained its DNA integrity and cellular structure through the increased expression of DNA damage repair and cell envelop synthesizing proteins and also progressively alleviated growth inhibition by 20% within two hours i.e., 6 h, by inducing the expression of antioxidative enzymes, production of unsaturated fatty acids, capsular and released exopolysaccharides and forming biofilm along with chemotaxis proteins. Conclusively, the adaptation of Anoxybacillus rupiensis TPH1 to lower temperature is mainly mediated by the synthesis of large numbers of defense proteins and exopolysaccharide rich biofilm formation.

Prospects of a hot spring-originated novel cyanobacterium, Scytonema ambikapurensis, for wastewater treatment and exopolysaccharide-enriched biomass production.

The present work performs the polyphasic characterization of a novel cyanobacterial species Scytonema ambikapurensis isolated from an Indian hot spring and evaluates its wastewater bioremediation potential. While the physicochemical analyses of the wastewater indicated high load of nutrients and metals, the wastewater bioremediation experiment performed using the test cyanobacterium denoted the removal of 70 and 86% phosphate, 49 and 66% sulfate, 96 and 98% nitrate, 91 and 92% nitrite, 95 and 96% ammonia, 66 and 72% chloride, 79 and 81% zinc, 68 and 80% nickel, 81 and 90% calcium, and 80 and 90% potassium from the autoclaved and un-autoclaved wastewater, respectively, after 20 days of culturing. The kinetics study of zinc and nickel removal from wastewater revealed that the cyanobacterium employed sequential biosorption (by following pseudo-second-order kinetics model) and bioaccumulation methods to remove these two metals. The quality of the autoclaved and un-autoclaved wastewater was further improved by the cyanobacterium through reduction of hardness by 74 and 81%, respectively. In wastewater, the cyanobacterium not only enhanced its biomass, chlorophyll and carbohydrate contents, but also produced small amount of released and high capsular exopolysaccharide (EPS). The FTIR and TGA analyses of capsular EPS unraveled that it was a negatively charged sulfated biomolecule having thermostability up to 240 °C, which suggested its possible use as excellent emulsifying, viscosifying, and biosorption agent. The credibility of this EPS as biosorption agent was ascertained by evaluating its metal chelating ability. Finally, the experimental data denoting the ability of S. ambikapurensis to bioremediate wastewater and simultaneously produce EPS was statistically validated by PCA1-pollutant removal model and the PCA2-cellular constituent model, respectively. Briefly, the study discloses that the cyanobacterium has huge biotechnological and industrial importance as it bioremediates wastewater and simultaneously produces thermostable exopolysaccharide.

Decoding whole genome of Anoxybacillus rupiensis TPH1 isolated from tatapani hot spring, India and giving insight into bioremediation ability of TPH1 via heavy metals and azo dyes.

A moderately thermophilic, gram-positive genomospecies Anoxybacillus rupiensis TPH1 was isolated from Tatapani hot spring, Chhattisgarh, India. Genome of 3.70 Mb with 42.3% GC subsumed 4131 CDSs, 65 tRNA, 5 rRNA, 35 AMR and 19 drug target genes. Further, comparative genomics of 19 Anoxybacillus spp. exhibited an open pan genome of 13102 genes along with core (10.62%), unique (43.5%) and accessory (45.9%) genes. Moreover, phylogenomic tree displayed clustering of Anoxybacillus spp. into two distinct clades where clade A species harbored larger genomes, more unique genes, CDS and hypothetical proteins than clade B species. Further, distribution of azoreductases showed FMN-binding NADPH azoreductase (AzoRed1) presence in clade A species only and FMN-binding NADH azoreductase (AzoRed2) harboring by species of both clades. Heavy metal resistance genes distribution showed omnipresence of znuA, copZ and arsC in both clades, dispersed presence of cbiM, czcD, merA and feoB over both clades and harboring of nikA and acr3 by few species of clade A only. Additionally, molecular docking of AzoRed1, AzoRed2, ZnuA, CopZ, Acr3, CbiM, CzcD, MerA and NikA with their respective ligands indicated high affinity and stable binding. Conclusively, present study provided insight into gene repertoire of genus Anoxybacillus and a basis for the potential application of this thermophile in bioremediation of azo dyes and heavy metals.