Data Paper |
Corresponding author: Tsveteslava Ignatova-Ivanova ( tsignatovaivanova@shu.bg ) Academic editor: Josef Settele
© 2022 Sevginar Ibryamova, Stephany Toschkova, Borislava Pavlova, Elitca Stanachkova, Radoslav Ivanov, Nikolay Natchev, Nesho Chipev, Tsveteslava Ignatova-Ivanova.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Ibryamova S, Toschkova S, Pavlova B, Stanachkova E, Ivanov R, Natchev N, Chipev N, Ignatova-Ivanova T (2022) A study of the microbiology of the intestinal tract in different species of Teleost fish from the Black Sea. BioRisk 18: 105-113. https://doi.org/10.3897/biorisk.18.80357
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This paper presents a study on the microbial status of different fish species and their habitats in the Bulgarian Black Sea area. The samples were collected in the period of January 2021 until March 2021. The fish species we used in this study were Black Sea turbot (Scophthalmus maximus), round goby (Neogobius melanostomus), shore rockling (Gaidropsarus mediterraneus) and European anchovy (Engraulis encrasicolus). The BIOLOG system was used for microbiological determination. From the different fish species, different species of microorganisms were isolated (using selective nutrient media). From the torbut, we isolated species Enterococcus villorum with 24 × 103 cells in 1 ml, Moraxella nonliquefaciens with 70 × 103 cells in 1 ml and Pseudomonas synxantha with 123 × 103 cells. Pseudomonas putida was isolated from the round goby with 20 × 103 cells in 1 ml. The species Streptococcus entericus with 123 × 103 cells in 1 ml was isolated from the shore rockling. Pseudomonas fulva with 60 × 103 cells in 1 ml was isolated from the European anchovy. A total of 223 × 103 cells in 1 ml of Pseudomonas agarici were isolated from Trachinus draco. Pseudomonas tolaasii with 145 × 103 cells in 1 ml were isolated from Merlangius merlangus. A different species of bacteria of the genus Pseudomonas was found for each of the investigated species of Black Sea fish. Apparently, the species Pseudomonas is characteristic of marine Teleostei and is important for the life and metabolism of these vertebrates. These microorganisms probably are resident species and developed not as result of pollution or environmental change.
marine fish, microbial status, intestinal tract
Fish are consumed in large quantities throughout the world and are considered one of the main sources of protein. According to
After their death, fish undergo rapid bacterial and microbiological changes, which are determining factors in their consumption by humans (
To date, data on the microbiota of fish in the Black Sea are very limited. Gaining information in this field is important as the sea can be a source of species of bacteria that are potentially dangerous to human health. The main goal of the present work was to study the microbiological composition of the intestinal tract in different species of Teleost fish from the Black Sea.
The fish individuals were randomly sampled from trawl catches using pelagic Midwater otter trawl (7 × 7 mm mesh size of the codend) from two localities of the Bulgarian Black Sea aquatory (Fig.
The fish were scrubbed free of dirt, washed in hypochlorite solution (20 mg/l), rinsed with sterile distilled water and shucked with a sterile knife. Tissue liquor samples (about 100 g) were homogenised (
The microbial identification was performed by the BIOLOG Microbial Identification System VIO45101AM. The isolated strains were screened on BL4021502 Tryptic Soy Agar (TCA), cultured for 24 hours at 37 °C and then subjected to Gen III plaque identification to identify Gram positive and Gram negative aerobic bacteria. The microscopic pictures were performed using the stereomicroscope OPTIKA (Italy) with a DinoEye, Eyepiece camera with 5 megapixels. The photographs were taken by using a Canon EOS 60D camera. The GEN III MicroPlate test panel provides a standardised micromethod using 94 biochemical tests to profile and identify a broad range of Gram-negative and Gram-positive bacteria. BIOLOG’s Microbial Identification Systems software (e.g. OmniLog Data Collection) is used to identify the bacterium from its phenotypic pattern in the GEN III MicroPlate. The BIOLOG system allows us to quickly and accurately identify more than 2900 species of aerobic and anaerobic bacteria, yeasts and fungi. BIOLOG’s advanced phenotypic technology provides valuable information on the properties of the strains, in addition to species-level identification. BIOLOG’s carbon technology identifies the environment and pathogenic microorganisms by producing a characteristic pattern or “metabolic fingerprint” of discrete test reactions performed in a 96-well microplate. The culture suspensions are tested with a panel of pre-selected assays, then incubated, read and compared with extensive data-bases. https://www.biolog.com/productsportfolio-overview/microbial-identification.
Using some classical microbiological methods, we investigated probes from the gastrointestinal tract of different species of fish from the Bulgarian Black Sea aquatory. After 24 h of cultivation on different media, the number of cells in 1 ml were obtained. The species of microorganisms were confirmed not only on selective media, but also by the results of the BIOLOG system. Data are represented in Table
Media/ fish | Pseudomonas agar | Streptococcus selective agar | Chromokult agar | MacConkey agar | strain BIOLOG |
---|---|---|---|---|---|
T26F1 Scophthalmus maximus –turbot–Varna | 24.103 | Enterococcus villorum | |||
Scophthalmus maximus – turbot – Varna | 70.103 | Moraxella nonliquefaciens | |||
Scophthalmus maximus – turbot – Varna | 123.103 | Pseudomonas synxantha | |||
T26F3 Neogobius melanostomus – round goby – Varna | 20.103 | Pseudomonas putida | |||
20T29-30F7 Platichthys flesus – shore rockling – Varna | 123.103 | Streptococcus entericus | |||
Engraulis encrasicolus – European anchovy Sozopol | 60.103 | Pseudomonas fulva | |||
20T10-11F2 Trachinus draco – greater wever – Varna | 223.103 | Pseudomonas agarici | |||
20T10-11F3 Merlangius merlangus – whiting–Varna | 145.103 | Pseudomonas tolaasii |
Stereomicroscope picture of the colonies of the isolated species in this case a E. villorum on media Chromocult agar and b P. agarici on media Pseudomonas agar. The picture was taken using the stereomicroscope OPTIKA (Italy) and DinoEye, Eyepiece camera, USB, 1.3 megapixsel, up to 5 megapixels.
For the present study, fresh Black Sea fish were used, which were dissected in laboratory conditions. The intestinal tract was used for microbiological analysis. Different species of microorganisms were isolated from the fish species using selective nutrient media (Table
The probable explanation for the difference in the species of microorganisms that were isolated from the intestine of the different fish species indicated that this may be due to the different habitats of fishes and their diet. In the winter months, the round goby lives at a depth of less than 60 m. The turbot is a predator and is found at a depth of 80 m buried in the sand. The flounder inhabits thin bottom layers at a depth of 50 m and feeds on crustaceans, worms and molluscs. The shore rockling feeds on “worms” and crustaceans, while the anchovy feed on plankton. According to
The microbiota of fish may be influenced by many factors, both endogenous and exogenous. Endogenous factors include the origin of the fish host (
According to data published very recently (
The question whether host-related microbiomes are primarily species-specific or depend on environmental factors still remains open. Our study is one of the few to focus on the intestinal microbiome of Black Sea fish species. It is interesting to note that the phylogenetic structure of the microbial communities of different fish is formed by species and habitat-specific factors. A different species of bacteria of the genus Pseudomonas was found for each of the investigated species of Black Sea fish. Apparently, Pseudomonas species are characteristic of marine Teleostei and are important for the life and metabolism of these vertebrates. These microorganisms are probably resident species and have developed not as result of pollution or environmental change. The presence of the species Enterococcus villorum and Moraxella nonliquefaciens, which are pathogenic species, may be due to pollutants of seawater, which settled in the sediment and infested the turbot in its natural habitat.
This study was financially supported by the National Research Fund of the Bulgarian Ministry of Education and Science (Grant – KP-06-PH41/2 28.09.2020) and the project by Shumen University project 08-80 / 09.02.2022 Department of Biology.