Abstract
This study presents a comparative analysis of halophiles from the global open sea and coastal biosystems through shotgun metagenomes (n = 209) retrieved from public repositories. The open sea was significantly enriched with Prochlorococcus and Candidatus pelagibacter. Meanwhile, coastal biosystems were dominated by Marinobacter and Alcanivorax. Halophilic archaea Haloarcula and Haloquandratum, predominant in the coastal biosystem, were significantly (p < 0.05) enriched in coastal biosystems compared to the open sea. Analysis of whole genomes (n = 23,540), retrieved from EzBioCloud, detected crtI in 64.66% of genomes, while cruF was observed in 1.69% Bacteria and 40.75% Archaea. We further confirmed the viability and carotenoid pigment production by pure culture isolation (n = 1351) of extreme halophiles from sediments (n = 410 × 3) sampling at the Arabian coastline of India. All red-pigmented isolates were represented exclusively by Haloferax, resistant to saturated NaCl (6 M), and had >60% G + C content. Multidrug resistance to tetracycline, gentamicin, ampicillin, and chloramphenicol were also observed. Our study showed that coastal biosystems could be more suited for bioprospection of halophiles rather than the open sea.
Highlights
The open sea and coastal biosystems were composed of 665 operational taxonomic units (OTUs)
A significant difference in the G + C content was observed between Haloarchaeal and Halobacterial isolates (Epps-singleton p = 6.3427 × 10−12 ) in line with the results reported in the literature [18,19]
The prevalence of MDR isolates observed in this study indicates the potential of antibiotic-resistant gene (ARG) horizontal transfer from environmental to clinically relevant pathogens [116,117,118]
Summary
Carotenoids synthesized by extreme halophiles are of specific interest for their ease in the extraction process, for saline tolerance, and for their biological applications against infectious diseases, repression of tumors or cancer growth, and cancer growth [3,4,5,6]. These extreme halophiles are mainly predominant in marine biosystems such as the open sea and coastal regions (salty marshes, salted ponds or similar ecosystems) [7]
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