The properties of intestinal bacteria/probiotics, such as cell surface hydrophobicity (CSH), auto-aggregation, and biofilm formation ability, play an important role in shaping the relationship between the bacteria and the host. The current study aimed to investigate the cell surface properties of fish intestinal bacteria and probiotics. Microbial adhesion to hydrocarbons was tested according to Kos and coauthors. The aggregation abilities of the investigated strains were studied as described by Collado and coauthors. The ability of bacterial isolates to form a biofilm was determined by performing a qualitative analysis using crystal violet staining based on the attachment of bacteria to polystyrene. These studies prove that bacterial cell surface hydrophobicity (CSH) is associated with the growth medium, and the effect of the growth medium on CSH is species-specific and likely also strain-specific. Isolates of intestinal lactobacilli from fish (Salmo ischchan) differed from isolates of non-fish/shrimp origin in the relationship between auto-aggregation and biofilm formation. Average CSH levels for fish lactobacilli and E. coli might were lower compared to those of non-fish origin, which may affect the efficiency of non-fish probiotics use in fisheries due to the peculiarities of the hosts’ aquatic lifestyles.

Background: The probiotics’ auto-aggregation and biofilm formation abilities have a significant role in the development of biotechnological processes.Objective: The aim of this study was to evaluate the biofilm formation and auto-aggregation abilities of novel, targeted aqua-probiotics isolated from aquatic organisms.Methods: The biofilm formation abilities of Lactobacillus delbrueckii str. UZ-1, Lactiplantibacillus plantarum str. R3, Lactococcus str. UZ-2, Enterococcus faecium str. R2, Pediococcus acidilactici str. N from the culture collection of the Microbiology of the Academy of Sciences of the Republic of Uzbekistan, Bacillus subtilis str. 1R, Bacillus amyloliquefaciens str. 4R and from the culture collection of the Southern Federal University of Russa and Lacticaseibacillus rhamnosus str. 1A and Enterococcus str. 9-3 from the culture collection of the Armenian National Agrarian University were assessed.Results: According to the investigations, the biofilm formation abilities of Lactobacillus delbrueckii str. UZ-1, Lactiplantibacillus plantarum str. R3, Lactococcus str. UZ-2, Enterococcus faecium str. R2, Pediococcus acidilactici str. N, Bacillus subtilis str. 1R, Bacillus amyloliquefaciens str. 4R, Bacillus amyloliquefaciens str. 5R, Lacticaseibacillus rhamnosus str. 1A and Enterococcus str. 9-3 were 0.119 ± 0.05D, 0.113 ± 0.065D, 0.196 ± 0.04D, 0.116 ± 0.01D, 0.152 ± 0.05D, 0.74 ± 0.15D, 2.621± 0.55D, 1.831 ± 0.45D, and 0.227 ± 0.04D and 0.483 ± 0.15D respectively. The highest rate of auto-aggregation was shown by Bacillus amyloliquefaciens str. 5R, and Bacillus amyloliquefaciens str. 4R was the strain with the highest ability to form biofilm. These two Bacillus strains are also distinguished by the highest DNA protective properties and relatively low antioxidant activity. Despite the fact that Bacillus amyloliquefaciens str. 5R showed the highest rate of auto-aggregation after 2 hours, this strain showed the lowest level of auto-aggregation among the studied strains after 24 hours. The Enterococcus str. 9-3 strain with the highest antioxidant activity showed 0.483 ± 0.15D biofilm formation ability.Conclusion: The novel targeted aquaprobiotics have distinct biofilm formation and aggregation properties, which are important to consider when planning appropriate biotechnological processes, requiring specific membrane properties of probiotics.Graphical Abstract: Membrane properties of novel targeted aquaprobiotics.Keywords: Lactobacilli, aqua-probiotic, antioxidant activity, biofilm formation, aggregation, Enterococcus str. 9-3

Lactic acid bacteria have a high potency to combat infections in the body. The range of lactic acid bacteria isolated from aquaculture in Uzbekistan has been described in this article. We found that Lactobacillus delbrueckii, L. plantarum, L. sakei, L. brevis, Lactococcus lactis, Pediococcus acidilactici, P. pentosaceus, Enterococcus faecium, E. hirae, E. mundii, E.faecalis, Leuconostoc citreum, and Weisella sibaria strains are represented in hydrobionts. Among them isolates Lactobacillus delbrueckii R1, Lactobacillus plantarum Kr5, Pediococcus acidilactici B, Enterococcus faecium R2, Lactobacillus plantarum R3, Pediococcus pentosaceus R1 showed high antagonistic activity against aquaculture pathogens. Four strains: Lactobacillus plantarum Kr5, Pediococcus acidilactici B, Enterococcus faecium R2, and Pediococcus pentosaceus R1, meet all the criteria for probiotics and can be recommended as part of probiotic feed additives.