Authors: Ahmed AlSubhi

Abstract

Background: Halophilic and halotolerant bacteria are potential sources of industrially important enzymes because of their ability to survive under hypersaline environmental conditions. Interest in extremophilic microorganisms for biotechnology has increased in recent years; however, limited information is available regarding the diversity and extracellular enzyme activity of halophilic bacteria along the Red Sea coastline, particularly in the Yanbu region of Saudi Arabia.

Methods: Thirty-five bacterial isolates were recovered from coastal seawater samples collected from the Red Sea coast at Yanbu, Saudi Arabia. The isolates were screened for extracellular enzyme activity, including amylase, cellulase, gelatinase, and protease production, using agar plate assays at 22 °C and 37 °C. Enzyme activity was evaluated using a semi-quantitative scoring system based on hydrolysis zone formation. Ten selected enzyme-producing isolates were subjected to partial 16S rRNA gene sequencing for molecular identification and phylogenetic analysis.

Results: Most isolates demonstrated at least one detectable enzyme activity, and several exhibited multiple enzyme activities. Gelatinase activity was the most frequently observed enzyme activity, followed by protease activity. Molecular identification revealed that most selected isolates belonged to marine-associated bacterial genera within the class Gammaproteobacteria, including Alteromonas, Pseudoalteromonas, and Vibrio, with sequence similarities ranging from 97% to 100%.

Conclusion: This study demonstrates the diversity of halophilic and halotolerant bacteria along the Yanbu coastline and highlights their extracellular enzymatic potential. The findings support further molecular and biotechnological investigations of marine halophilic bacteria from the Red Sea region. The observed extracellular enzyme activities may also have biomedical relevance in future enzymatic and biofilm-related applications.

Keywords: Halophilic bacteria, Red Sea microbiome, enzyme activity, 16S rRNA sequencing, Yanbu.