ABSTRACT

Actinobacteria exist in different habitats, such as soil, lakes, compost, sewage environments, and terrestrial, marine, and freshwater. They are also found in extreme habitats of the marine sediments and highly alkaline and saline environments, displaying complex stress management mechanisms for their survival. The phylum Actinobacteria contains a large number of genera with some novel species capable of growing in extreme habitats. The molecular basis of their adaptation in various extreme environments mainly includes the role of different transporter proteins and osmolytes, which maintain an isotonic internal environment. The actinobacteria are Gram positive and largely include mesophilic groups. The existence and diversity of the actinobacteria in extreme niches has recently gained the attention of the scientific community. Chemotaxonomic characterizations, along with different fingerprinting methods, are the key parameters to studying the diversity and distribution of the actinobacteria. The assessment of phylogeny based on single-gene analysis and the whole genome using different bioinformatics tools can offer abundant evolutionary information. Actinobacteria are well known to produce chemically diverse compounds of a wide range of biological activities. They are the key producers of antibiotic and numerous bioactive compounds and enzymes of commercial significance. This chapter focuses on the aspects of the diversity, distribution, and adaptation of the cultivable haloalkaliphilic actinobacteria.