Bacterial community of Vardar chub (Squalius vardarensis): Preliminary results

Anthropogenic activities increase discharge of different pollutants in the aquatic environment which cause deterioration of the environment. Mining activities release in the environment different inorganic species and metals, which has negative effects on the water quality, aquatic organisms and humans. Aquatic organisms are affected by metal concentrations not only in their surrounding water but also in their food. Microorganisms are also affected by changes in the environment and can also provide biological responses to the environmental disturbances. Microorganisms associated with aquatic organisms can thus be used to monitor the impact of mining activities on the aquatic environment because of the ubiquity of microorganisms in aquatic environments. The objectives of the present study were (i) to determine abundance of fish bacterial population and species diversity of bacterial community of Vardar chub (Squalius vardarensis) from three Macedonian rivers, (ii) to compare obtained bacterial communities, and (iii) to isolate and characterize the isolates using different methods of bacterial identification (MALDI and VITEK 2 Systems), and (iv) to evaluate whether they provide a good assessment of the potential detrimental effects of pollution on aquatic organisms. For that purpose, we sampled 68 fish from rivers: Zletovska (12), Bregalnica (30) and Kriva (26), and obtained samples for bacteriological analysis from the gills and internal organs (spleen, liver and kidney). According to bacterial analysis Kriva and Bregalnica Rivers are aquatic environments under high anthropogenic influence. In contrast, Zletovska River constitutes a less microbial polluted ecosystem. Bacterial analyses were negative for internal organs, whereas samples form the gills were only positive. Bacterial analysis of gills indicated that size of the bacterial population were higher in fish from the Bregalnica River (10.8 CFU/fish) in relation to Kriva (7.2 CFU/fish) and Zletovska River (7 CFU/fish). Contribution of bacterial genera to the bacterial population assemblage was higher in Zletovska River, with three genera: Pseudomonas (52%), Aeromonas (24%) and Acinetobacter (24%), more than in relation to Kriva River, two genera: Pseudomonas and Morganella, as well as to Bregalnica River with one genus Acinetobacter. This study reveals the influence of microbial water quality on diversity of fish bacterial populations in the rivers. In general, dominant genera Pseudomonas and Acientobacter, which are known as genera that can remove metals and have bioaccumulation potentials for metals from polluted aquatic environments, can provide a good assessment for the determination of the potential effects of metal pollution on the aquatic organisms.