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1.
Traditional culture‐based technique and 16S rDNA sequencing method were used to investigate the mucosa‐associated autochthonous microbiota of grass carp (Ctenopharyngodon idellus). Twenty‐one phylotypes were detected from culturable microbiota, with Aeromonas, Shewanella, Lactococcus, Serratia, Brevibacillus, Delftia, Pseudomonas, Pantoea, Enterobacter, Buttiauxella and Yersinia as their closest relatives. Genomic DNA was directly extracted from the gut mucosa of C. idellus originating from six different geographical regions, and used to generate 609 random bacterial clones from six clone libraries and 99 archaeal clones from one library, which were grouped into 67 bacterial and four archaeal phylotypes. Sequence analysis revealed that the intestinal mucosa harboured a diversified bacterial microbiota, where Proteobacteria, Firmicutes and Bacteroidetes were dominant, followed by Actinobacteria, Verrucomicrobia and Deinococcus‐Thermus. The autochthonous bacterial communities in the gut mucosa of fish from different aquatic environments were not similar (Cs < 0.80), but γ‐Proteobacteria was a common bacterial class. In comparison to bacterial communities, the archaeal community obtained from one library consisted of Crenarchaeota and Euryarchaeota. These results demonstrate that molecular methods facilitate culture‐independent studies, and that fish gut mucosa harbours a larger bacterial diversity than previously recognized. The grass carp intestinal habitat selects for specific bacterial taxa despite pronounced differences in host environments.  相似文献   

2.
ABSTRACT

Quantitative levels of six known pathogens (Listeria monocytogenes, Clostridium botulinum, Salmonella species, Vibrio cholerae, Yersinia enterocolitica, and Y. pseudotuberculosis) and aerobic plate counts were measured at five aquaculture facilities. The farmed rainbow trout (Oncorhynchus mykiss) and trout fillets were sampled at two different growing seasons to monitor for microbial hazards. Listeria spp. was identified in both whole trout and trout fillets from all five facilities sampled from both growing seasons. Presumptive Clostridium botulinum spores were also identified from all five facilities for both seasons. The growing season did not affect pathogen levels and there was no evidence that any one aquacultural system was superior to the others. Salmonella spp., Vibrio cholerae, and Yersinia spp. were not isolated from any of the trout samples analyzed.  相似文献   

3.
The concept of the use of probiotic organisms or prebiotic compounds to modify the fish gut microflora is becoming a popular topic for investigation. A major flaw in many such studies is a failure to consider fully the nature of the established microflora, which is to be modified pre-, or probiotically. Since it is widely accepted that a large proportion of bacteria are non-culturable, the use of conventional bacteriological (culture) techniques alone to investigate fish intestinal microflora may be expected to bias results. We report a study designed to investigate the normal intestinal microflora of rainbow trout (Oncorhynchus mykiss) using both conventional bacteriological and molecular methods.Over an 18 month period, the intestinal microflora of a single population of laboratory-raised rainbow trout was investigated. Bacteria isolated using bacteriological techniques were identified using the BiOLOG system and 16S rRNA gene sequencing. Dominant bacteria consistently were Aeromonas sp. and Carnobacterium piscicola, demonstrating that the microflora is stable in fish kept in defined conditions. Restriction Fragment Length Polymorphism (RFLP) and 16S rRNA gene sequence analysis was used to investigate anaerobic and non-culturable bacteria. An obligate anaerobe, Clostridium gasigenes, was shown to be among the dominating intestinal microflora.  相似文献   

4.
A study was conducted to evaluate the probiotic properties of endogenous rainbow trout microbiota against pathogenic Lactococcus garvieae. A total of 335 bacterial strains were isolated from rainbow trout and screened for antagonistic activity against L. garvieae using an agar spot assay. Antagonistic strains were grouped by PCR amplification of repetitive bacterial DNA elements (rep‐PCR) and identified by 16S rRNA gene sequence analysis. The results revealed that the antagonistic strains belonged to the genera Lactobacillus, Lactococcus and Leuconostoc. Further probiotic characteristics, such as specific growth rate, doubling time, resistance to biological barriers, antibiotic resistance, hydrophobicity and production of antimicrobial substances, were also studied. These strains were able to survive low pH and high bile concentrations, showed good adherence characteristics and a broad spectrum of antibiotic resistance. The antagonistic efficacy was maintained after sterile filtration and was sensitive to proteinase K, indicating that proteinaceous extracellular inhibitory compounds were at least partially responsible for pathogen antagonism. Based on these results, these strains should be further studied to explore their probiotic effects in challenge experiments in vivo. This study shows clear evidence that the indigenous trout‐associated microbiota may provide a defensive barrier against L. garvieae.  相似文献   

5.
A study was conducted to evaluate the probiotic effect of Pediococcus acidilactici MA18/5M on rainbow trout, Oncorhynchus mykiss. Fish (310 ± 9 g) were fed a control diet or a P. acidilactici‐supplemented diet (at 2.4 × 106 CFU/g) for 4 weeks. The probiotic was observed to populate the intestine with levels ranging from log 3.7 to 5.4 CFU/g. Furthermore, these populations were able to persist for at least 24 hr after the cessation of probiotic feeding. High‐throughput sequencing analysis of bacterial 16S rRNA libraries demonstrated that P. acidilactici was able to modulate the gut microbiome of rainbow trout and that the probiotic was detected as a common taxon on the mucosa and in the digesta of the probiotic fish (p < .05). Real‐time polymerase chain reaction demonstrated that feeding the probiotic upregulated pro‐inflammatory cytokines, interleukin‐1β, and interleukin‐8 and downregulated anti‐inflammatory interleukin‐10 compared to the control‐fed fish. Furthermore, the mRNA levels for the mucosal antibody immunoglobulin T was also elevated in probiotic‐fed fish. These findings help to explain some of the mechanisms behind the previously reported observed benefits of using this probiotic in the intestinal morphology and immunity of rainbow trout.  相似文献   

6.
Serum and mucosal antibody responses of juvenile rainbow trout, Oncorhynchus mykiss, were characterized by enzyme‐linked immunosorbent assay (ELISA) following immunization with various preparations of formalin‐killed Flavobacterium psychrophilum cells. The protective nature of these preparations was then determined by immunizing rainbow trout fry and challenging with the bacterium. Juvenile rainbow trout immunized intraperitoneally (i.p.) with formalin‐killed F. psychrophilum emulsified with Freund's complete adjuvant (FCA), and i.p. with formalin‐killed F. psychrophilum either with or without culture supernatant generated significant serum antibody responses by 6 and 9 weeks, respectively. Significant mucosal antibody responses were detected by 9 weeks only in fish immunized i.p. with killed F. psychrophilum/FCA. Following immunization and bacterial challenge of rainbow trout fry, protective immunity was conferred in F. psychrophilum/FCA and saline/FCA groups with relative per cent survival values of up to 83 and 51, respectively. Significant protection was not observed in treatment groups immunized by immersion or i.p. without adjuvant at the challenge doses tested. Results suggest that stimulation of non‐specific immune factors enhances the ability of fish to mount a protective immune response, but specific antibody appears necessary to provide near complete protection. In this study, an ELISA was developed to monitor anti‐F. psychrophilum antibody production in trout. The relationship of such responses to protective immunity suggests that future vaccination strategies against coldwater disease may require stimulation of both the innate and adaptive arms of the immune response.  相似文献   

7.
Bacterial communities from the intestinal tract of rainbow trout were investigated to assess transient and resident microbial communities using both culture-based and culture-independent techniques. Viable counts attached to the intestinal mucosa were in the range of log 4.77–5.38 and log 6.67–6.79 CFU g−1 in the intestinal contents. Pseudomonas spp. and Enterobacteriaceae constituted nearly 80% of the allochthonous population but <60% of the autochthonous populations. This coincided with an elevated mucosal level of a group of Gram-positive rods from ∼2% in the digesta to 25–35% on the mucosa. This group was identified by 16S rRNA as Arthrobacter aurescens and Janibacter spp. HTCC2649. Analysis of denaturing gradient gel electrophoresis banding patterns showed complex communities in all intestinal regions. Similarity coefficients showed that mucosal communities were ∼70% similar to digesta communities and yet due to the presence of bands found uniquely either in the digesta or on the mucosa, the communities are distinctly different. Scanning electron microscopy confirmed mucosal bacterial populations and highlighted a possible localized colonization between mucosal folds. The study highlights the complexity of resident microbial communities that have not been fully explored in previous rainbow trout studies; this is especially true with probiotic/prebiotic investigations.  相似文献   

8.
The mechanisms by which nonnative species establish populations can be classified into two broad categories: they usurp the niches of native species through interspecific competition, or they avoid this intense interspecific competition by making use of minimal niche overlap with the native species. In this study, we considered how a nonnative salmonid species, the rainbow trout Oncorhynchus mykiss, established a population in the presence of the native salmonid species, the masu salmon O. masou, in Hokkaido, Japan. Circumstantial field evidence shows that the masu salmon exceeds the rainbow trout in abundance and suggests that these species use different types of cover habitat (rainbow trout abundance increases with increasing abundance of large woody debris aggregates, whereas masu salmon abundance increases with increasing abundance of undercut banks). These results imply that the rainbow trout established a population due to minimal niche overlap with the masu salmon, and not by competitive exclusion of the native species.  相似文献   

9.
A study was conducted to analyze the effects of snails (Physa gyrina) on biofilm, bacterial abundance, off-flavor-producing bacteria, and off-flavor compounds in reuse aquaculture systems culturing rainbow trout (Oncorhynchus mykiss). Eight experimental-scale systems were used, including four with and without snails. Mean heterotrophic bacteria counts in water were lower (P < 0.05) in systems with snails. Submerged surfaces of sumps containing snails were nearly biofilm-free, while sumps without snails were coated with biofilm. Geosmin levels in trout fillets from snail-stocked systems were generally lower but not statistically different from the controls. Rainbow trout health and performance was not affected by snail presence.  相似文献   

10.
A study was conducted to characterize the autochthonous gut microbiota present in the pyloric caeca (PC), anterior mucosa (AM) and posterior mucosa (PM) of brown trout (Salmo trutta). Total viable counts (TVC) bacterial populations were enumerated using tryptone soy agar, lactic acid bacteria (LAB) levels were enumerated on de Man, Rogosa & Sharpe agar and PCR‐DGGE was employed as a culture‐independent method to assess the total communities. No significant differences were observed between the different gut regions for TVC or LAB levels. 16S rRNA sequencing identified all LAB isolates as Carnobacterium maltaromaticum. In contrast, the TVC community was more diverse; Firmicutes and Bacteroidetes were present but all gut regions were dominated by Proteobacteria, accounting for 88.4–92.6% of the communities. Citrobacter freundii was the dominant species and accounted for 51.0–57.8% of the isolates. Complex bacterial communities were observed using PCR‐DGGE and a trend towards the reduction in the number of operational taxonomic units (OTUs), microbial richness and microbial diversity was observed from the PC to the PM. The similarity between regions was low (52–68%) and cluster analysis revealed that the communities grouped into two distinct clusters; one dominated by the PM samples and the other contained the AM and PC samples. OTUs from the DGGE were identified as members of the phyla Proteobacteria and Firmicutes. Many OTUs were detected in all gastrointestinal regions, however, some OTUs showed regional specialization. Further studies are required to elucidate the activity of these genera in situ and how their actions impact the host.  相似文献   

11.
The effect of dietary probiotics (Bacillus subtilis, Bacillus licheniformis and Enterococcus faecium) used singularly and synergistically on the growth performance, intestinal microbiota and health status of rainbow trout (Oncorhynchus mykiss Walbaum) were assessed after 10 weeks feeding on supplemented diets. No significant improvements of weight gain or specific growth rate were observed in the probiotic fed groups. However, a significant improvement of feed conversion ratio was observed in the group fed E. faecium. High levels of probiotic species were observed in the posterior gastrointestinal tract as transient digesta‐associated populations and potentially resident mucosal populations. Bacillus subtilis and B. licheniformis levels accounted for 36% of the total culturable microbial population adhered to the mucosa and 62% in the digesta. E. faecium levels accounted for 45% of the mucosal population and 89% of the population in the digesta. An increase of serum lysozyme activity was observed in the fish fed diets containing the Bacillus probionts and elevated leukocyte levels were observed in fish fed diets containing Bacillus + E. faecium synergistically. The results of the current study demonstrate potential for B. subtilis, B. licheniformis and E. faecium to improve feed utilization, modulate intestinal microbiota and the health status of rainbow trout.  相似文献   

12.
In this study, high throughput 16S rRNA sequencing was used to investigate the effect of a novel whole‐cell dietary microalgae meal (Schizochytrium limacinum), on the distal intestinal microbiome of farmed rainbow trout, Oncorhynchus mykiss. Heterotrophic microalgae are rich in omega 3 polyunsaturated fatty acids, can be produced sustainably and have been shown to have beneficial effects on host health. After a 15‐week trial period, microbial community profiles were compared between the distal intestinal contents of fish fed either a control diet or a treatment diet that partially replaced fish oil with microalgae meal, at a substitution level of 5%. The results of this research showed that the microbial communities of both fish populations were composed of similar microbial taxa, however, the treatment group fed the microalgae supplement possessed a greater level of microbial diversity than those in the control group. A limited number of bacterial taxa were discriminatory between diets and were significantly elevated in the treatment group, notably operational taxonomic units (OTUs) assigned to the genera Streptococcus, Leuconostoc, Lactobacillus, Lactococcus and Weissella. However, the overall structure of the intestinal microbiome between control and treatment groups was not found to be significantly different. The treatment group displayed a heavier mean weight and condition factor at the end of the trial period. The results of this study suggest that the tested microalgae meal can be used as a replacement for a proportion of fish oil in aquafeeds, with minor changes to the intestinal microbiome of farmed rainbow trout, and positive effects on growth.  相似文献   

13.
In this study, 318 bacterial strains were isolated from the gastrointestinal (GI) tracts of 29 rainbow trout, Oncorhynchus mykiss (Walbaum). These bacteria were screened in vitro for their ability to inhibit growth of Flavobacterium psychrophilum, the causative agent of coldwater disease. Bacteria observed to inhibit F. psychrophilum growth were further screened against rainbow trout bile, as an indicator of their ability to survive in the GI tract. This screening resulted in narrowing the pool to 24 bacterial isolates. Those 24 isolates were then tested for pathogenicity in rainbow trout by intraperitoneal injection. Following a 28‐day challenge, eight isolates were shown to cause direct mortality and were eliminated from further study. As a result, 16 bacterial isolates were identified as probiotic candidates with the potential to control or reduce disease caused by F. psychrophilum.  相似文献   

14.
An enteritic syndrome affecting farmed rainbow trout and occurring predominantly in summer has recently been described and related to the massive accumulation of a segmented filamentous bacterium (SFB), ‘Candidatus Arthromitus’, in the digestive tract of fish. Details of the clinical manifestations, the characteristics of the bacterium and the possible aetiology of the disease are presented in this paper. No other bacterial pathogen than ‘Candidatus Arthromitus’ was characterized in trout undergoing the enteritic syndrome. From clinical and histopathological observations, a toxin or toxic product accumulation was suspected in affected trout, and could account for the massive destruction of the intestinal mucosa. However, the origin and aetiological role of the SFB could not be clearly elucidated, although most of the filaments appeared to beviable and to produce and release strings of endospores in the lumen of the gut. The organism could not be cultured in the conditions tested, shared several morphological and structural characteristics with related bacteria described in the intestinal microflora of different vertebrate species, but no attachment structure was definitively recognized. All attempts to detect similar SFB in the fish diet orin the environment of affected fish farms were unsuccessful. It is unclear whether this organism represents a normal and not previously detected inhabitant of the intestine of trout stressed after environmental perturbation, or whether it results directly from external sources of contamination.  相似文献   

15.
In the winters of 1995 and 1996, unusual disease outbreaks occurred on two separate channel catfish farms in Arkansas, USA. Affected fish exhibited extraordinary haemorrhaged rings around the eyes and raised haemorrhaged areas overlying the frontal foramens. Other signs included abnormal swimming, lethargy, loss of equilibrium, and exophthalmia. Bacterial isolates from the moribund fish were identified as Yersinia ruckeri by biochemical tests, no lysis by the Hafnia-specific bacteriophage 1672, and Y. ruckeri-specific growth patterns on Shotts-Waltman media. Fingerling catfish injected intraperitoneally with the bacterial isolate at 7.8 × 106 bacteria fish?1 developed lesions characteristic of the epizootics at 13, 18, and 22 °C and a biochemically identical isolate was recovered. Fingerling rainbow trout injected with the channel catfish isolate at 1 × 105 bacteria fish?1 and held at 20 °C developed signs typical of enteric redmouth by 4 days post-inoculation and were moribund by 5 days post-inoculation. Some differences of clinical signs occurred between experimentally infected rainbow trout and channel catfish. Clinical and biochemical similarities between infections of Y. ruckeri and many warmwater pathogens in affected catfish may lead to incorrect diagnosis of ERM infections.  相似文献   

16.
The non‐native rainbow trout (Oncorhynchus mykiss) has been introduced worldwide for angling purposes and has established self‐reproducing populations in many parts of the world. Introduced rainbow trout often have negative effects on the native salmonid species, ranging from decrease abundance, growth and survival, to their local extinction. Assessing the effects of introduced rainbow trout on the native species is thus crucial to better set up conservation programmes. In this study, we investigated the effects of non‐native rainbow trout on the diet of native marble trout (Salmo marmoratus) living in the Idrijca River (Slovenia). An impassable waterfall separates the stream in two sectors only a few hundred metres apart: a downstream sector (treatment) in which marble trout live in sympatry (MTs) with rainbow trout (RTs) and an upstream sector (control) in which marble trout live in allopatry (MTa). Specifically, we investigated using stable isotopes the effects of rainbow trout on dietary niche, diet composition, body condition, and lipid content of marble trout. We found dietary niche expansion and niche shift in marble trout living in sympatry with rainbow trout. Compared to MTa, MTs had higher piscivory rate and showed higher body condition and prereproduction lipid content. Our results indicate that the presence of rainbow trout did not have negative effects on marble trout diet and condition and that changes in dietary niche of marble trout are likely to be an adaptive response to the presence of rainbow trout, and further research is needed to better understand.  相似文献   

17.
黏膜及其表面的共生菌群是鱼类抵御外界不利环境的第一道屏障。为探索养殖罗非鱼表皮和鳃黏膜共生菌菌群的结构特征是否与其健康状况间存在相关关系,本研究运用高通量测序技术,以无乳链球菌腹腔注射攻毒48 h后存活和濒死尼罗罗非鱼为检测对象,检测攻毒前后罗非鱼表皮和鳃黏膜共生菌群落结构差异。结果显示,健康尼罗罗非鱼表皮和鳃黏膜共生菌均存在优势菌群,主要为特吕珀菌属、硫杆菌属、弓形杆菌属、海单胞菌属和弧菌属。人工感染无乳链球菌后存活尼罗罗非鱼表皮和鳃黏膜共生菌菌群与感染前无显著差异;与存活组相比,濒死尼罗罗非鱼的表皮和鳃黏膜共生菌菌群多样性下降,其中弓形杆菌属、假交替单胞菌属、海单胞菌属、假单胞菌属和弧菌属等含量显著下降,链球菌属含量占总菌群的55.30%±1.24%,表明养殖尼罗罗非鱼表皮和鳃黏膜共生菌群落结构可能与其健康状况相关。  相似文献   

18.
Animal digestive tract is habitat for a large number of autochthonous microbiota, which play central roles in multiple biological and physiological processes of the host. In this study, two different micro‐biomass preparation methods were employed to evaluate the diversity of intestinal mucosa‐associated microbiota in grass carp (Ctenopharyngodon idellus). Genomic DNAs were isolated either directly from intestinal mucosal samples (group A), or from micro‐biomass after microbial dissociation (group B). Community richness, diversity and evenness indices were all higher in group B, but differences were not statistically significant (P = 0.97, P = 0.33, P = 0.34 respectively). Furthermore, group B samples exhibited an increased ratio of bacterial DNA in comparison with group A samples, but the difference was also not statistically significant (P = 0.74). In addition, there were no statistically significant differences between the two groups (P > 0.05) at the taxonomic level. Our results support previous findings that there exists a great abundance of the intestinal mucosa‐adherent microbiota in the grass carp; among these, Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, Spirochaetes and Fusobacteria were the most common phyla. Within these microbiota, Paenibacillus, Bacteroides, Bacillus and Cetobacterium genera comprise the majority of the community, implicating their functional importance (e.g. as probiotics) to their host. Our results contribute towards a better understanding of the intestinal microbial profile of grass carp. Both micro‐biomass preparation techniques proved to be feasible for studying mucosa‐adherent microbiota of grass carp; however, the second method (group B) provides a protocol that is somewhat more effective than the first method (group A).  相似文献   

19.
A feeding experiment was conducted to study the response of rainbow trout juveniles fed different levels of lupin meal in diets for rainbow trout juveniles. Very limited information is available on the relationship between dietary lupin meal in rainbow trout health status. Therefore, this study aimed to determine the effects of lupin meal inclusion levels (0%, 15%, 30%, 45%, and 60%) on growth performance and health status of rainbow trout juveniles. The experimental diets (LM0, LM15, LM30, LM45, and LM60) were formulated iso‐nitrogenous (41% crude protein) and iso‐calorific (18% crude lipid). The fish were fed twice a day. As a result, the best growth performance was observed in fish fed with LM15 and LM30 diets. No significant differences were detected among experimental groups in terms of body compositions. The haematological values showed significantly (p < 0.05) lower heamatocrit and mean cellular volume (MCV) in the group of LM60 compared with the other groups. For the other haematological parameters such as haemoglobin, red blood cell and mean cellular haemoglobin studied in the present study no significant differences were observed (p < 0.05). The lupin meal included groups showed significant reduction in total protein (TPROT), triglyceride (TROG), cholesterol (CHOL), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH) compared with the control group (p < 0.05). The inclusion of lupin meal did not cause any changes in glucose (GLU), glutamic oxaloacetic transaminase (GOT), and glutamic pyruvic transaminase (GPT) between the treatment groups (p < 0.05). In conclusion, lupin meal might be used in rainbow trout diets up to 30% without any malnutrition effect on growth performance, haemotological and serum biochemical parameters.  相似文献   

20.
哈尼梯田稻鲤共作模式下的微生物群落结构   总被引：2，自引：0，他引：2  
为了探究哈尼梯田稻鲤共作模式(复合生态系统)微生物菌落结构特征,本实验拟采用高通量测序技术对稻鲤共作(RC)与稻田单作(CK)2种模式下水体、表层以及根系土壤及鲤肠道细菌(16S rDNA)多样性特征进行分析。高通量测序结果显示,复合生态系统中主要细菌门类为变形菌门、放线菌门、厚壁菌门、绿弯菌门、酸杆菌门、拟杆菌门及硝化螺旋菌门等。与CK相比,RC表层土壤中绿弯菌门和厚壁菌门相对丰度显著增加,主要显著增加的优势菌属为厌氧绳菌(Anaerolineaceae_norank)、Aminicenantes_p_norank、未定义的绿弯菌(Chloroflexi_P_unclassified)、梭菌(Clostridium_sensu_stricto_1)、梭菌(C._sensu_stricto_12)、互营菌(Syntrophaceae_f_norank)、芽单胞菌(Gemmatimonadaceae_f_norank);RC根系土壤中绿弯菌门含量显著高于CK组,主要是Anaerolineaceae_norank、Sideroxydans、Aminicenantes_p_norank、Chloroflexi_p_unclassified、Gemmatimonadaceae_f_norank优势菌属显著增加。RC模式中鲤肠道优势菌主要为厚壁菌门和变形菌门,其中厚壁菌门相对丰度为58.59%,超过一半的丰度。RC模式组相比CK组,土壤的有机质、总氮、总磷等理化指标都有所降低,其中pH、总磷和速效磷显著降低;稻田表层和根系土壤的细菌Sobs指数及PD指数也均增加,其中稻田表层土壤组显著增加。研究表明,增加鲤养殖后,稻田表层土壤的理化性质和细菌群落结构产生明显变化,同时也在一定程度上对水稻根系和养殖生物肠道的群落结构产生了影响。本研究初步揭示了RC复合生态系统优于CK系统的微生物生态基础。  相似文献   

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