Antimicrobials: Shift from Conventional to Extreme Sources

*Aasif Majeed Bhat, Qazi Parvaiz Hassan and Aehtesham Hussain*

#### **Abstract**

Antimicrobials- the chemical substances that inhibit the growth of microorganisms and stop their multiplication are immensely useful in the context of pathogenic microorganisms where these substances either contain their growth by inhibiting them from growing (bacteriostatic) or killing them permanently (bacteriocidal). They may broadly be either antibiotics, antifungals, antivirals and antiparasitics. A major class of antimicrobials are antibiotics and almost half of the total percent of antibiotics driven from microbials are sourced from different taxonomic levels of actinomycetota (formerly actinobacteria), significantly from the genus Streptomyces. Adaptability and mechanisms to resist drug effects has outpushed the evolution of drug resisitant pathogenic microorganisms and outnumbered their growth vis a vis the discovery of new antimicrobials. Gone is the golden age of antibiotics: the tussle between antimicrobials to resist the growth of pathogens and the latter to contain the inhibitory effects of former has largely weighed on the pathogenic side- thanks to the inefficient and excessive use of antibiotics and their misapplication. Growth of drug (multi-drug) resistant pathogens coupled with inadequate antibiotics has set a dire need to explore new habitats-aquatic, terrestrial and microbiomes associated as endophytes in other plants and animals. The shift in habitat selection from conventional to extreme locations is met with convincingly successful outcomes. Researchers successfully explore the actinomycetota drug discovery potential of deep sea oceans, extreme high altitude Himalayas that remain capped with snow and glaciers round the year. The abyssopelagic and glaciated peaks both share similarity in that they are constrained by different pressure parameters. The environmental pressures associated with deep pelagic oceans are partial to complete exclusion of light, lack of phothosynthesis and associated vegetation, limited nutrition and hydrostatic pressure by thounsands of pounds per square inch. Mountain peaks are glaciated, ice cold with limited nutrition and oligotrophic in nature. These temperature constraints in both the aquatic and terrestrial environments have activated the drug expression secondary metabolite machinary of actinomycetota to kill or inhibit other microorganisms and spare the already limited resources for their own growth. This antibiotic secretion paradigm also applies to actinomycetota living as endophytes in an interactive dynamic environments with insects and other organisms. The antibiotic potential hidden in these extreme selected sites is worthy of killing the microbial bugs and conatining the ever growing resistant pathogen load. Successful exploitation strategies should be hastened to garner the antimicrobial potential of these extreme sources.

**Keywords:** antimicrobials, antibiotics, drug discovery, Actinomycetota, Actinobacteria, extreme habitats, NRPS and PKS
