Isolation and Identification of Gut Bacteria from Wild Humphead Wrasse (Cheilinus undulatus) in Semporna, Malaysia Reveals Potential Pathogens and Health-Associated Taxa

The humphead wrasse (Cheilinus undulatus), an endangered coral reef species, shows aquaculture potential for conservation, yet limited data exist on its cultivation. This study characterizes the culturable gut bacterial community in wild specimens collected from Semporna, Malaysia, using selective culture-dependent techniques combined with full-length 16S rRNA gene Sanger sequencing. Fourteen distinct, non-redundant bacterial species were successfully identified. These included emerging fish pathogens and opportunistic taxa of clinical or zoonotic relevance, such as Proteus mirabilis, Vagococcus lutrae, and Atlantibacter hermannii. Concurrently, health-associated beneficial bacteria, including Bacillus cereus and Lactococcus lactis, were also recovered from the cohort. Because samples were pooled during plating to optimize broad-spectrum recovery, these isolates establish a qualitative collective checklist of the cohort's culturable taxa. These findings highlight both potential opportunistic disease risks and strategic opportunities for microbiome-based health management in humphead wrasse aquaculture, underscoring the necessity of robust welfare management and targeted dietary interventions during captive rearing.