Bacterial Diversity and Antibiotic Resistance Genes Associated with the Different Farming Systems of Black Tiger Shrimp (Penaeus monodon) in Bangladesh

Microbial community inhabiting the intestine of the shrimp (Penaeus monodon) and their surrounding environments (e.g., water and sediment) is considered as a key contributing factor for the sustainable farming of shrimp. Indiscriminate application of antibiotics in aquaculture is a growing concern due to the emergence of antibiotic resistant bacteria (ARB), more specifically the antibiotic resistance genes (ARGs). The present study investigates the microbiome composition and 19 ARGs from four different shrimp farming systems; (i) cluster, (ii) extensive, (iii) semi-intensive, and (iv) improved extensive in the southwest coastal region of Bangladesh. In doing so, the study applied advanced 16S rRNA-based metagenomic sequencing to study the bacterial composition. Moreover, gene specific polymerase chain reaction (PCR) was employed to detect the ARGs in shrimp, water, and sediments of different farming systems. In the current study, bacteria from the phylum Proteobacteria and Firmicutes were predominant among the samples (n = 12) collected from the different farming systems followed by Actinobacteria, Bacteroidetes, and Cyanobacteria. Firmicutes was the predominant phylum in the gut of shrimp cultured in the cluster (relative abundance 53.33%) and semi-intensive (relative abundance 59.2%) culture systems. Results indicated that the bacterial community structure was significantly ( $p<0.05$ ) distinct among gut, sediment, and water samples as well as the farming systems. The shared operational taxonomic unit (OTU) in the sediment sample (16,495) was nearly double than the gut (7,931) and water (8,513) bacterial communities. The improved extensive farming system showed 1,289 (11.05%) shared OTUs among gut, sediment, and water followed by semi-intensive (6.87%), cluster (6.27%), and extensive (5.46%) farming system. Among the tested ARGs, sul1, cat, gyrA(C), tetA, tetC, tetX, ere(A), vanR, and dfrA1 were predominant in water and sediment samples. Semi-intensive farming system had the highest prevalence of ARGs (21.05%) while the lowest prevalence was found in extensive (5.26%) farming system. Overall, the study provides a comprehensive scenario of bacterial composition and growing emergence of ARGs in shrimp farming of Bangladesh. Therefore, the production strategy must focus on the alternatives of antibiotic for shaping the shrimp cultivation technique more sustainable.