Rhodothalassium (Rts.) salexigens is a halophilic purple nonsulfur bacterium and the sole species in the genus Rhodothalassium, which is itself the sole genus in the family Rhodothalassiaceae and sole family in the order Rhodothalassiales (class Alphaproteobacteria). The genome of this phylogenetically unique phototroph comprises 3.35 Mb and is highly chimeric, with nearly half of its genes originating from families other than the Rhodothalassiaceae, many of which lack phototrophic species. Photosynthesis genes in Rts. salexigens are not arranged in a typical photosynthesis gene cluster but are scattered across the genome, suggesting an origin from horizontal transfers. Despite an encoded RuBisCO, autotrophy has not been observed in Rts. salexigens, and enzymes that oxidize common inorganic electron donors are not encoded. Phospholipid biosynthesis in Rts. salexigens is restricted, and phosphoglycerolipids are the only phospholipids present in its intracytoplasmic membranes. Rts. salexigens fixes nitrogen using a Mo-containing nitrogenase and uses ammonia despite previous results that indicated it was a glutamate auxotroph. Glycine betaine is the sole osmolyte in Rts. salexigens, and enzymes are encoded that facilitate both its uptake and its biosynthesis from glycine. The genomic data also support chemotactic swimming motility, growth over a range of salinities, and the production of membrane-strengthening hopanoids.

The enzymology of the key steps in the archaeal phospholipid biosynthetic pathway has been elucidated in recent years. In contrast, the complete biosynthetic pathways for proposed membrane regulators consisting of polyterpenes, such as carotenoids, respiratory quinones, and polyprenols remain unknown. Notably, the multiplicity of geranylgeranyl reductases (GGRs) in archaeal genomes has been correlated with the saturation of polyterpenes. Although GGRs, which are responsible for saturation of the isoprene chains of phospholipids, have been identified and studied in detail, there is little information regarding the structure and function of the paralogs. Here, we discuss the diversity of archaeal membrane-associated polyterpenes which is correlated with the genomic loci, structural and sequence-based analyses of GGR paralogs.

Halocins, the proteinaceous antimicrobial agents produced by haloarchaea, may be used for the preservation of salted foods and the treatment of diseases. For their application and function explanation, it is necessary to produce the active recombinants. In this work, a haloarchaeal strain producing halocin was isolated from the salt-fermented shrimp and identified as Natrinema sp. RNS21 by 16S rRNA gene sequence analysis. From 1 L of RNS21 culture, about 0.32mg of halocin with 96% purity was obtained. Based on the molecular weight, stability and amino acid sequence alignment, the antimicrobial peptide belonged to the halocin C8 (HalC8) family. HalC8 was expressed by fusion with glutathione-S-transferase (GST) in E. coli, followed by affinity purification and enterokinase (EK) cleavage. About 6.2mg of recombinant HalC8 with 95% purity was obtained from 1 L of E. coli culture. MALDI-TOF-MS and RP-HPLC analysis indicated that the molecular weight and folding pattern of purified recombinant HalC8 were the same as those of native HalC8. Recombinant HalC8 showed obvious inhibitory activity against Haloferax volcanii. Contrast to native HalC8, the active recombinant HalC8 could be easily produced in a short time with a high yield.

The current century has witnessed an unimpeded and exponential surge in the population leading to overexploitation of natural resources generating enormous amount of waste in different forms. Fossil fuels have been the major source of energy since the last century, which are depleting at a very fast pace, creating environmental pollution and have resulted in a steep rise in global warming. In recent times, globally, the scientific fraternity have put their efforts tirelessly for the recognition and development of wastewater treatment technologies not only for the generation of carbon-neutral and eco-friendly energy, but also for resolving the issue of wastewater disposal that are given paramount importance to fulfil the burgeoning demands of energy and environment protection. Considering wastewater only as a source, the energy potential contains in it could be five-times more than the energy consumed to treat it. A generation of bioenergy from wastewater with simultaneous treatment reduces the overall cost and makes the whole process environmentally sustainable. This chapter discusses the promising and sustainable technical approaches which are being employed to treat the wastewater for harnessing energy through the biological route and environment protection, and other also futuristic scope for industrial growth.

Acidic water, rich in minerals generated by dissolution of metallic ores, is accelerated by metabolic activities of indigenous microbes that results in the formation of acid mine drainage (AMD) which often causes severe metal pollution in the areas adjoining to the mines. The acidophilic microorganisms indigenous to the geogenous ore bodies are the driving factor in an acid mine. Primarily two categories of microbes cause acidification of ores depending on its nature. The sulfurous ores harbor some autotrophic bacteria that bring about its dissolution, whereas the non-sulfurous ores have a group of heterotrophic microbes that indirectly produce acid and result in liquefaction of the available metals. This process of metal solubilization, commonly called bioleaching, is a very interesting field of scientific research as it can be used as an alternative of traditional mining techniques in an eco-compatible way. These acidophiles comprise a surprisingly wide diversity of microorganisms. The current chapter discusses the biodiversity of acidophilic microbes and their metabolic activities that result in the generation of AMD and the application of these acidophiles in metal bioleaching.

The current study describes a novel species with the strain name ERMR1:05T isolated from the forefield soil of East Rathong Glacier in West Sikkim Himalaya (India). The isolate was facultatively anaerobic, gram-stain negative, non-spore-forming, rod-shaped, and oxidase negative. Whole-genome-based bacterial core gene phylogenetic analysis placed the strain in the genus Rahnella, well separated from Rouxiella spp. The digital DNA-DNA hybridisation and average nucleotide identity values between strain ERMR1:05T and other members of genus Rahnella were below the proposed thresholds for the species delineation. Based on these results, a new species, Rahnella sikkimica sp. nov., is proposed with strain ERMR1:05T (CIP 111636T, MTCC 12598T) as the type strain. The bacterium showed upregulation of cold-stress genes in cold conditions. Additionally, the genome analysis of the bacterium showed the presence of plant growth-promotion factors suggesting its role in crop improvement in cold hilly regions.

In the context of using lignocellulosic biomasses as second-generation raw materials, there is no single versatile microbe known to date that can completely hydrolyze all the biomasses available, since biomass compositions are highly variable from site to site and even season to season. The most attractive biomass conversion technologies will be those that are insensitive to fluctuations in feedstock and are robust in the face of biologically challenging process-operating conditions. Given these specifications, it makes sense to consider microorganisms that grow at extreme temperatures, and enzymes derived from them, for key roles in biomass conversion processes. Many microorganisms that grow at elevated temperatures are able to utilize a variety of carbohydrates pertinent to the conversion of lignocellulosic biomass to bioenergy. One such group of microorganisms are Geobacillus spp. in which nature has optimized multi-enzyme processes for growth substrate acquisition. In nature, Geobacillus spp. have evolved and adapted their physiology via genome diversification through fortuitous mutations, transposable elements, and horizontal gene transfer so as to develop the communal capacity to use available growth substrates in their environs. The members of this genus provide thermostable enzymes and can be used for deconstruction of biomasses applications at elevated temperatures; therefore, these organisms are of biotechnological importance. In this book chapter, insights into the enzymology and the capability of this genus to degrade lignocellulosic through the analysis of Geobacillus genomes as well as pan genomes are discussed.