Gut microbiota analysis of Blenniidae fishes including an algae-eating fish and clear boundary formation among isolated Vibrio strains

Abstract

Some marine fishes are algae-feeding, and the microorganisms in their digestive tracts produce carbohydrate hydrolyzing enzymes such as agarose and fucosidase, which are potentially interesting resource for new functional enzymes. The purpose of this study was to establish a method for identifying and utilizing characteristic bacteria from the intestines of two algae-eating fish species: Andamia tetradactylus, which exclusively eats algae on the rock surface, and stellar rockskipper Entomacrodus stellifer, which feeds on both algae and invertebrates. We tested the species composition of the intestinal bacterial flora and found that Proteobacteria were commonly found both in species as in the common gut communities of marine fish, whereas Spirochaetes and Tenericutes occupied the flora of A. tetradactylus. We then performed anaerobic and aerobic cultures and isolated 34 and 44 strains including 48 strains belonged to Vibrio species from A. tetradactylus and E. stellifer. We observed that some Vibrio strains formed a clear boundary to avoid contacting other strains of bacteria. Whole-genome sequencing of such two Vibrio alginolyticus strains revealed two cyclic chromosomes commonly found in the genome of Vibrio species, and some unique genes encoding alginate lyase, chitinases, and type I-F CRISPR-associated endoribonuclease for the first time in Vibrio alginolyticus.

The variation of intestinal autochthonous bacteria in cultured tiger pufferfish Takifugu rubripes

“…Spirochaetes forms a monophyletic phylum of bacteria and has several genera that contain pathogenic species, which could lead to intestinal spirochetosis ( Hampson and Ahmed, 2009 ). Spirochaetes was commonly detected in the digestive tracts of arthropods and several species of mammals and regularly found deep in marine sediments and soils, but at low concentrations in the intestinal microbiota of fish ( Yoshida et al., 2022 ). The Spirochaetes abundance in the seawater in OSCS system was extremely lower than that in the intestine samples in this study, suggesting that the high abundance of Spirochaetes in the intestine samples in OSCS system was not caused by the passive transfer from seawater but possibly due to the active selection by fish.…”

Fish disease and intestinal microbiota: A close and indivisible relationship

“…42 The type of diet also influences the composition of the microbiota. Cellulose-degrading bacteria, Clostridium, Citrobacter and Leptotrichia, are dominant in herbivores 43 ; meanwhile, protease-producing bacteria, such as Halomonas and Cetobacterium are in carnivores. 38 In this regard, an aerobic bacterial community thriving in the GIT of freshwater teleosts, including grass, silver, mrigal and common carps (Ctenopharyngodon Idella, Hypophthalmichthys molitrix, Cirrhinus cirrhosus and Cyprinus carpio), catla (Catla catla), rohu (Labeo rohita), tilapia (Oreochromis), walking catfish (Clarias batrachus) and murrel (Channa striata), provide enzymatic activities such as amylase, cellulase, lipase and protease, essential for food degradation and assimilation.…”

Emerging Research Topics in the Vibrionaceae and the Squid–Vibrio Symbiosis

“…Examining how agar catabolism shapes host-microbe associations between the Vibrionaceae and red algae is a fascinating endeavor worth pursuing. Such effects are likely to cascade to higher trophic levels and impact community ecology at large [ 166 , 167 ].…”