Expression and Function of ABC Proteins in Fish Intestine

In fish, the intestine is fundamental for digestion, nutrient absorption, and other functions like osmoregulation, acid-base balance, and excretion of some metabolic products. These functions require a large exchange surface area, which, in turn, favors the absorption of natural and anthropogenic foreign substances (xenobiotics) either dissolved in water or contained in the food. According to their chemical nature, nutrients, ions, and water may cross the intestine epithelium cells’ apical and basolateral membranes by passive diffusion or through a wide array of transport proteins and also through endocytosis and exocytosis. In the same way, xenobiotics can cross this barrier by passive diffusion or taking advantage of proteins that transport physiological substrates. The entry of toxic substances is counterbalanced by an active efflux transport mediated by diverse membrane proteins, including the ATP binding cassette (ABC) proteins. Recent advances in structure, molecular properties, and functional studies have shed light on the importance of these proteins in cellular and organismal homeostasis. There is abundant literature on mammalian ABC proteins, while the studies on ABC functions in fish have mainly focused on the liver and, to a minor degree, on the kidney and other organs. Despite their critical importance in normal physiology and as a barrier to prevent xenobiotics incorporation, fish intestine’s ABC transporters have received much less attention. All the ABC subfamilies are present in the fish intestine, although their functionality is still scarcely studied. For example, there are few studies of ABC-mediated transport made with polarized intestinal preparations. Thus, only a few works discriminate apical from basolateral transport activity. We briefly describe the main functions of each ABC subfamily reported for mammals and other fish organs to help understand their roles in the fish intestine. Our study considers immunohistochemical, histological, biochemical, molecular, physiological, and toxicological aspects of fish intestinal ABC proteins. We focus on the most extensively studied fish ABC proteins (subfamilies ABCB, ABCC, and ABCG), considering their apical or basolateral location and distribution along the intestine. We also discuss the implication of fish intestinal ABC proteins in the transport of physiological substrates and aquatic pollutants, such as pesticides, cyanotoxins, metals, hydrocarbons, and pharmaceutical products.

Isolation of Aeromonas sobria JC18 from milkfish (Chanos chanos) intestine with proteolytic and cellulolytic activities for fish probiotic

Attention on the probiotic application for the improvement of fish resident intestinal microbiota has risen in the last decades. It is demonstrated that probiotics may function not only by direct inhibition of pathogenic bacteria or manipulation of enzymatic digestion of feed but also by modulation of immunity in fish. In the present study, we aimed to isolate the autochthonous microbiota of marine fish intestines as probiotic candidates based on cellulolytic and proteolytic activity. Bacteria were isolated and purified on a cellulose agar with 24h of incubation. A total of 18 bacterial strains were purified and stored in -80°C. Phenotypic screening based on the antibiotic resistance, antagonistic activity against pathogenic bacteria, resistance to an acidic environment, and ability of colonization in fish intestine found a selected strain, namely JC18. Infection test, molecular and phenotypic characterizations revealed that the JC18 isolate was a non-pathogenic Aeromonas sobria. It is hence revealed that the milkfish intestine is a potent source of proteolytic bacteria for fish probiotic screening.

Effects of Nisin, Cecropin, and Penthorum chinense Pursh on the Intestinal Microbiome of Common Carp (Cyprinus carpio)

Following a ban on antibiotic use in the feed industry, trials on the effects of various immunostimulants (prebiotics, probiotics, antimicrobial peptides [AMPs], and herbs) on the survival, growth, immunity, and disease control of farmed fish in aquaculture are being rapidly conducted. The wide variety of microbes with roles in nutrition, metabolism, and immunity in the fish intestine is the primary factor affecting the fermentability and functionality of dietary immunostimulants. For this reason, the dynamic interactions between immunostimulants and the intestinal microbiome may influence fish health. In this study, the effects of two agriculturally important AMPs (nisin and cecropin) and one herb (Penthorum chinense) on the gut microbiome of common carp were investigated, using 16S rDNA high-throughput sequencing. The results suggest that all three substances can alter the richness, diversity, and composition of the intestinal microbiota of common carp. P. chinense had a similar effect on the gut microbiota of common carp to that of nisin, and both promoted more striking changes in the gut microbiota community than did cecropin. The relative abundance of Proteobacteria was lower in the nisin and P. chinense groups than in the control and cecropin groups. The relative abundance of Bacteroidetes in the nisin, cecropin, and P. chinense groups was markedly increased, compared with that of the control group. Additionally, nisin, cecropin, and P. chinense showed obvious anti-inflammatory effects on the fish intestine, which was reflected by significantly increasing the expression levels of two anti-inflammatory cytokines IL-10 and TGF-β. Some digestive enzyme activities in the fish intestine were also significantly enhanced by supplementing these three substances in feeds.

Acanthocephalan Worms Mitigate the Harmful Impacts of Heavy Metal Pollution on Their Fish Hosts

Toxic metal pollutants in aquatic environments and infestationwith intestinal helminths adversely affect the fish health, as well as fish consumers. Acanthocephalan worms in fish intestine have a high potential to absorb and bioaccumulate different heavy metals, especially toxic ones, from the intestine via their tegument with greater efficiency than the fish intestinal wall. Herein, 47 specimens of the fish Siganusrivulatus were trapped in the Red Sea, Egypt, from a chronically polluted bay. All were intoxicatedwith Cd and Pb; 20 (42.5%) were uninfected with any intestinal worm, but the other 27 (57.5%) were infected only by the intestinal acanthocephalan Sclerocollum rubrimaris. The number of individual worms in a fish host (infrapopulation size) ranged from 32 to 236. As a reference group, 22 uncontaminated–uninfected specimens of S. rivulatus were trapped from a small unpolluted bay. Our results revealed that infection with acanthocephalans alleviatesthe harmful effectsof toxic metalson their fish hosts by: (1) lowering the elevated concentrations of both Cd and Pb in fish liver; (2) lowering the elevated levels of liver enzymes (ALT, AST, ALP, and GGT), glucose, triglycerides, and urea in fish blood serum; and (3) raising the declined levels of total protein and albumin in fish blood serum. All of these were dependent on S. rubrimaris infrapopulation size in fish intestine.

Fish disease study of Asian seabass (Lates calcarifer) in a floating marine cage: Endoparasite and blood profile

Hidayati D, Nurindra AR, Abdulgani N, Setiawan E, Maulidina N, Syahroni N, Mulyadi Y. 2021. Fish disease study of Asian seabass (Lates calcarifer) in a floating marine cage: Endoparasite and blood profile. Biodiversitas 22: 4505-4511. The Indonesian government has multiple targets and priority programs to increase aquaculture productivity in 2021. Hence, the development of mariculture commodities such as Asian seabass (Lates calcarifer) in one of the potential coastal areas, Sendang Biru, is strategic. However, sustainable productivity needs good management, including the health monitoring of fish. This study aimed to determine the condition of seabass under mariculture in a floating cage in Sendang Biru, Malang, Indonesia. Thirty seabass (Lates calcarifer) from 0 to 60 days after stocking age (ASE) were taken from a Sendang Biru floating cage. Blood and intestine samples were taken five times from day 0 to day 60 ASE. Blood samples were carried out through the caudal vein and observed using a hemocytometer. Endoparasite analysis was performed by fish intestine examination from the anterior intestine to the posterior rectum. Pseudoterranova and Diphyllobothrium were found with 10% and 3.33% prevalence, respectively. The intensity of Pseudoterranova was one individual/fish, and that of Diphyllobothrium was 2.33 individuals/fish. The highest mean of total erythrocyte count (TEC) found in 0 day ASE was at the level of 0.82±0.55×106 cells/mm3, and the lowest was found in 60 days ASE (0.51±0.24×106 cells/mm3). The highest mean of total leucocyte count (TLC) was 9.20±3.69x104 cells/mm3, at day 0, and leukocyte levels tended to decrease until day 60 ASE (7.74±3.43×104 cells/mm3). Overall, despite the TEC and TLC tending to decrease from 0 to 60 days ASE, in statistically indicated no significant differences in TLC at different ASEs (p > 0.05). The hematological profile indicated the health statuses of the cultured Asian seabass in the current study were in a condition of anemic and infected.

Fishmeal Replacement with Hermetia illucens Meal in Aquafeeds: Effects on Zebrafish Growth Performances, Intestinal Morphometry, and Enzymology

Fishmeal (FM) is still the most important protein source in aquafeeds. However, due to the reduction of wild fish stocks used for FM production, its manufacturing it is now unsustainable. Insect meal represents a valid alternative to FM, due to the low carbon footprint of its production and its high nutritional value. The aim of this study was to investigate the potentials of replacing FM with black soldier fly (Hermetia illucens) meal (HIM) in aquafeeds, using zebrafish as the animal model. Four diets were formulated with increasing HIM/FM replacement rate (the control diet contained 20% FM). Mortality rates, growth performances, and feed consumptions were measured, and fish intestine samples were collected for histological and enzymatic analysis. After 49 days, all groups almost tripled their initial body weight (cumulative body weight gain ranged between 143.9 and 155.2 mg), and no statistically significant differences among treatments were observed in relation to growth performances and histological traits. Contrarily, trypsin, alkaline phosphatases, and alpha amylase–glucoamylase activities were significantly reduced when the FM replacement rate was increased. In conclusion, HIM may represent an alternative to FM, since no adverse effects were observed when it was included up to 20% in the zebrafish diet, even when replacing 100% of the FM.

Draft Genome Sequence of Deefgea sp. Strain CFH1-16, Isolated from the Intestine of the Freshwater Fish Hypomesus nipponensis

ABSTRACT Reported here is the draft genome sequence of Deefgea sp. strain CFH1-16, isolated from the intestine of a Hypomesus nipponensis fish collected from the Republic of Korea. The genome sequence was assembled into two contigs with 48.2% G+C content. These genome data could improve our understanding of adaptation in the fish intestine.

Comparative Bacteriological Evaluation of Frozen and Salt Water Tilapia Fishes (Oreochromos niloticus and Oreochromos aureus) Sold in Port Harcourt, Rivers State Nigeria

Fishes are highly perishable, and prone to vast variations in quality due to differences in species, feeding habits as well as the environmental and preservation factors. This study Compared the bacteriological quality of Frozen and Salt Water Tilapia Fishes (Oreochromos niloticus and Oreochromos aureus) sold in Port Harcourt, Nigeria. Total number of sixty (60) samples were evaluated. Frozen tilapia (36) and salt water tilapia fishes (24) were obtained from the three sampling markets using sterile bags which were properly labelled. The samples were transported to the Laboratory for analyses within 2 hours of collection in a thermos box containing ice pack and standard microbiological procedures were employed in the bacteriological evaluations. Different parts of the fishes such as Intestine, gills and flesh of the samples were dissected and used for bacteriological analysis. Statistical analyses were carried out using ANOVA and All pairs tukey- kramer. Results obtained from the study showed that the highest number of total heterotrophic bacteria count was obtained from frozen fish gills which was 7.7 x 106±0.98 cfu/g while the least count of 4.7 x 106±0.67 cfu/g was from salt water tilapia fish flesh. Total coliform count ranged from 3.3 x104±0.91 cfu/g to 8.0 x104±0.44a cfu/g for salt water flesh and frozen fish intestine from different markets respectively. Listeria species count ranged from 1.3 x104± 0.30 cfu/g to 4.3 x104±0.57 cfu/g for salt water fish intestine and frozen fish flesh respectively. Total Salmonella count ranged from 1.0 x103±0 cfu/g to 6.2x103±1.30cfu/g for frozen fish flesh and salt water fish intestine. These values were above the WHO permissible limit. Mean values for all the microbial counts were significantly different at (P<0.05) in the two samples across the sampled markets comparatively, frozen fish has more bacteriological load than salt water fish, this may be attributed to the handling, hygiene storage of the respective fishes as well as storage conditions. Listeria species were identified as L. monocytogenes, L. graji, L. seeligeri, L. ivanovii, and L. welshmeri by genomic studies. While three species of Salmonella such as S. arizonae, S. gallinarum, S. typhi were isolated. Other bacterial isolates were identified as Vibrio spp, Bacillus spp Staphylococcus spp Shigella spp Pseudomonas spp. Enterobacter spp. E. coli, Micrococcus spp. Acinetobacter spp. Klebsiella spp. This study revealed that fish sold at different markets in Port Harcourt especially frozen fish, is highly contaminated with different kinds of bacterial pathogens which may constitute potential public health hazard due to the unhygienic nature of fish vendors which predisposes frozen fishes to contamination by pathogenic microorganisms. Therefore proper blanching and heating methods should be employed during preparations of fishes to avoid cross contamination and food intoxication/ poisoning before consumption. It is important that all hazard analysis critical control point be adhered to for good production processes.