Characterization of Micrococcus luteus and Bacillus marisflavi Recovered from Common Dentex (Dentex dentex) Larviculture System

Abstract

In this manuscript, thirty yellow-pigmented Gram-positive bacteria were isolated from natural intestine microflora and from sea water around the marine cage of a rearing tank of common dentex (Dentex dentex), in the Aegean Sea on the Turkish coast and were characterized. Eighteen isolates were assigned to the species Micrococcus luteus, the other twelve to the species Bacillus marisflavi. Eight representative strains, six from B. marisflavi and two from M. luteus, were chosen for further 16S rDNA analyses. A pathogenicity assay for the isolated bacterial strains was carried out in rainbow trout and it evidenced absence of pathogenicity in the tested strains. The isolated strains were tested for in vitro antagonistic activity against Listonella anguillarum, a pathogen bacterium diffused in Mediterranean aquaculture and affecting various fish species. The isolated bacterial strains showed antagonistic activity against the pathogenic bacterium, suggesting a possible role of isolates as probiotics. In this study, for the first time, bacterial strains of the species B. marisflavi, known as an environmental species, were recovered in the gut microbiota of a healthy fish. The use of the isolates characterized in this study, mainly the yellow-pigmented bacterium, is suggested as possible probiotics to improve fish health, along with alternative methods of maintaining a healthy environment.

Effects of Dietary Fishmeal Replacement by Poultry By-Product Meal and Hydrolyzed Feather Meal on Liver and Intestinal Histomorphology and on Intestinal Microbiota of Gilthead Seabream (Sparus aurata)

“…Similar findings have been reported for Salmo salar [41] with authors stating that the role of fish-hosts in selecting or promoting core microbes is unclear. Actinobacteria species were dominant and unique in the HFM fed fish and their dominance could be related to their antimicrobial functions (i.e., antibiotics) that protect the host [53,54]. Additionally, the prevalence of terpenoid biosynthesis genes that were prevalent in the HFM fed fish is mostly detected in Actinobacteria [55] and was in accordance with the taxonomic BCC (Figure 7A,B).…”

A Repeating Sulfated Galactan Motif Resuscitates Dormant Micrococcus luteus Bacteria

“…Solid substrates also have been reported to induce morphological changes (31), antibiotic production (32), and activation of two-component signal transduction pathways (33). M. luteus is ubiquitously distributed and is well known to thrive in marine environments, among many other habitats (34). Sulfated galactans are produced by a wide variety of organisms, including a large diversity of seaweeds but also marine plants and animals (35).…”

A novel bacterial infection in cultured Nile tilapia, Oreochromis niloticus in New Valley, Egypt

“…This difference in prevalence may be attributed to the difference in water temperature, stocking density and water quality. M. luteus has been described as a natural member of the aquatic environment and the intestinal microflora of various fish species (Akayli et al, 2016 andAkayli et al, 2019) and as an emerging opportunistic pathogen (Pękala et al 2018). So, its isolation from the diseased O. niloticus in this study may be related to fish immunity which decreased by the effect of different stressors present in the farms.…”