Family Aeromonadaceae Research Articles

Interactions between Balantidium ctenopharyngodoni and microbiota reveal its low pathogenicity in the hindgut of grass carp

BackgroundHosts, parasites, and microbiota interact with each other, forming a complex ecosystem. Alterations to the microbial structure have been observed in various enteric parasitic infections (e.g. parasitic protists and helminths). Interestingly, some parasites are associated with healthy gut microbiota linked to the intestinal eubiosis state. So the changes in bacteria and metabolites induced by parasite infection may offer benefits to the host, including protection from other parasitesand promotion of intestinal health. The only ciliate known to inhabit the hindgut of grass carp, Balantidium ctenopharyngodoni, does not cause obvious damage to the intestinal mucosa. To date, its impact on intestinal microbiota composition remains unknown. In this study, we investigated the microbial composition in the hindgut of grass carp infected with B. ctenopharyngodoni, as well as the changes of metabolites in intestinal contents resulting from infection.ResultsColonization by B. ctenopharyngodoni was associated with an increase in bacterial diversity, a higher relative abundance of Clostridium, and a lower abundance of Enterobacteriaceae. The family Aeromonadaceae and the genus Citrobacter had significantly lower relative abundance in infected fish. Additionally, grass carp infected with B. ctenopharyngodoni exhibited a significant increase in creatine content in the hindgut. This suggested that the presence of B. ctenopharyngodoni may improve intestinal health through changes in microbiota and metabolites.ConclusionsWe found that grass carp infected with B. ctenopharyngodoni exhibit a healthy microbiota with an increased bacterial diversity. The results suggested that B. ctenopharyngodoni reshaped the composition of hindgut microbiota similarly to other protists with low pathogenicity. The shifts in the microbiota and metabolites during the colonization and proliferation of B. ctenopharyngodoni indicated that it may provide positive effects in the hindgut of grass carp.

A pilot study on the isolation and identification of histamine-producing bacteria from narrow barred Spanish mackerel and Japanese thread fin bream from Ukkadam fish market, Coimbatore, India

Consumption of marine fishes with high histamine levels due to improper storing leads to cause scombroid or histamine fish poisoning. In spoiled fishes, bacteria begin to break down the histidine into histamine by decarboxylation activity. Previous studies reported that black muscle fishes usually produce large amounts of histamine-producing bacteria (HPB). In this study, two white muscle fishes such as Scomberomorus commerson (Narrow-barred Spanish mackerel) and Nemipterus japonicus (Japanese threadfin bream) were chosen to detect the presence of histamine-producing bacteria (HPB). The fish samples were purchased from Ukkadam fish market in Coimbatore and examined for the occurrence of HPB on Niven agar. The isolated HPB on media were analyzed for identification based on their morphological characteristics, primary test, and biochemical test. Finally, 8 colonies were confirmed as the cause for histamine production of both fishes and among them, 5 belong to the family Enterobacteriaceae and others belong to the family Aeromonadaceae, Morganellaceae, and Enterococcaceae. Our study showed that the histamine-producing bacteria highly reported in dark-muscle fishes were also isolated from the chosen white-muscle fishes. Hence the presence of HPB indicates the improper maintenance of fish in retail fish markets. This considerable incidence of histamine-producing bacteria which on proliferation under suitable conditions may contribute to toxic histamine accumulation in the flesh of fishes.

Genome‐wide insights into whole gut microbiota of rainbow trout, Oncorhynchus mykiss, fed plant proteins and camelina oil at different temperature regimens

AbstractGut microbiota impacts fish metabolism, nutrient utilization, and health. We know little about how temperature and diet interact with rainbow trout gut microbes. A total of 288 fish (average body weight: 45.6 g) fed four iso‐caloric, ‐lipidic, and ‐nitrogenous diets comprised crude protein (40%) and lipid (20%) manufactured as 100% animal‐based protein (AP) and blend of 50 fish oil (FO)/50 camelina oil (CO), 100% AP and 100% CO, 100% plant‐based protein (PP) and blend of 50 FO/50 CO or 100% PP and 100% CO at 14 or 18°C water temperature. Gut content was analyzed using 16S rRNA gene and shotgun sequencing. Alpha‐diversity did not change significantly. Regardless of diet, Tenericutes, Firmicutes, Proteobacteria, Spirochaetes, Bacteroidetes, and Actinobacteria dominated. At family level, Aeromonadaceae and Enterobacteriaceae dominated at 18°C, while Mycoplasmataceae dominated at 14°C. Moreover, genes relating to amino acid, carbohydrate, fat, and energy metabolisms and fatty acid biosynthesis significantly increased at 18°C. Functional profiles did not vary significantly among diets, except for a higher methionine and cysteine metabolism in fish fed plant ingredient compared animal diet, suggesting trout fed plant‐derived protein mixed with CO could be as effective as those fed fish meals mixed with 50/50 FO and CO.

Changes in the intestinal microbiota of farmed northern sheatfish (Silurus soldatovi) associated with natural bacterial infection

AbstractAn acute infectious disease of northern sheatfish (Silurus soldatovi) was found in a commercial aquaculture pond in Tianjin, China. Herein, two dominant bacterial strains were isolated from naturally diseased northern sheatfish and identified as Aeromonas veronii and Vibrio cholerae. Seven healthy and seven naturally diseased fish that were collected from the pond were used for the gut microbiota analysis by high‐throughput 16S rRNA gene sequencing. The α‐diversity indices (ACE, Chao 1, and Shannon) did not differ significantly between diseased and healthy fish (p > 0.05), but a significant separation was observed between them when β‐diversity analysis of the bacterial population was performed. The diseased fish demonstrated a significant elevation in the relative abundances of Aeromonas, Vibrio, Blautia, and Megamonas and a decrease in Cetobacterium, Bacteroides, Chryseolinea, Ralstonia, and Pseudomonas compared with healthy fish (p < 0.05). Linear discriminant analysis effect size showed that microbial marker species in the diseased fish were in the order Aeromonadales, the family Aeromonadaceae, and the genus Aeromonas. The functional profiles of the microbial community that were predicted using the PICRUSt2 indicated that the disturbance of gut microbiota caused the alteration of its functional profiles in the diseased fish.

Fermented Wheat Bran Polysaccharides Improved Intestinal Health of Zebrafish in Terms of Intestinal Motility and Barrier Function

Intestinal barrier dysfunction and gut microbiota disorders have been associated with various intestinal and extraintestinal diseases. Fermented wheat bran polysaccharides (FWBP) are promising natural products for enhancing the growth performance and antioxidant function of zebrafish. The present study was conducted, in order to investigate the effects of FWBP on the intestinal motility and barrier function of zebrafish, which could provide evidence for the further potential of using FWBP as a functional food ingredient in the consideration of gut health. In Experiment 1, the normal or loperamide hydrochloride-induced constipation zebrafish larvae were treated with three concentrations of FWBP (10, 20, 40 μg/mL). In Experiment 2, 180 one month-old healthy zebrafish were randomly divided into three groups (six replicates/group and 10 zebrafish/tank) and fed with a basal diet, 0.05% FWBP, or 0.10% FWBP for eight weeks. The results showed that FWBP treatment for 6 h can reduce the fluorescence intensity and alleviate constipation, thereby promoting the gastrointestinal motility of zebrafish. When compared with control group, zebrafish fed diets containing FWBP showed an increased villus height (p < 0.05), an up-regulated mRNA expression of the tight junction protein 1α, muc2.1, muc5.1, matrix metalloproteinases 9 and defensin1 (p < 0.05), an increased abundance of the phylum Firmicutes (p < 0.05), and a decreased abundance of the phylum Proteobacteria, family Aeromonadaceae, and genus Aeromonas (p < 0.05). In addition, 0.05% FWBP supplementation up-regulated the intestinal mRNA expression of IL-10 and Occludin1 (p < 0.05), enhanced the Shannon and Chao1 indexes (p < 0.05), and increased the abundance of Bacteroidota and Actinobacteriota at the phylum level (p < 0.05). Additionally, 0.1% FWBP supplementation significantly improved the villus height to crypt depth ratio (p < 0.05) and increased the mRNA expression of IL-17 (p < 0.05). These findings reveal that FWBP can promote the intestinal motility and enhance the intestinal barrier function, thus improving the intestinal health of zebrafish.

A review on aeromoniasis in poultry: A bacterial disease of zoonotic nature

Aeromonas spp. are widely distributed in surface water, sewage, untreated and chlorinated, drinking water, as well as meats, fish, shellfish, poultry, and their products. A disease caused by Aeromonas spp. is designated as aeromoniasis. It can affect different aquatic animals, mammals, and birds in different geographic regions. Moreover, gastrointestinal and extra-intestinal disease conditions may be provoked in humans as a result of food poising with Aeromonas spp. Some Aeromonas spp. have been identified, however, Aeromonas hydrophila (A. hydrophila), A. caviae, and A. veronii bv sobria may be of public health significance. Aeromonas spp. are members of family Aeromonadaceae and genus Aeromonas. They are Gram-negative rod-shaped, facultative anaerobic, and oxidase and catalase-positive bacteria. The pathogenicity of Aeromonas in different hosts is mediated by several virulence factors such as endotoxins, cytotoxic enterotoxin, cytotoxins, hemolysins, adhesins, and extracellular enzymes such as proteases, amylases, lipases, ADP-ribosyltransferases, and DNases. Most avian species are susceptible to either natural or experimental infections with Aeromonas spp. Infection usually arises through feacal-oral route. Traveler's diarrhea as well as other systemic and local infections are the clinical picture of food poisoning associated with aeromoniasis in humans. Despite Aeromonas spp. being sensitive to various antimicrobials, multiple drug resistance has been commonly reported worldwide. Accordingly, this review highlights aeromoniasis in poultry regarding Aeromonas virulence factors epidemiology, pathogenicity, zoonosis, and antimicrobial resistance.

Change in gut histomorphology and microbiota in Chinese strip‐necked turtle hatchlings

The development of the digestive system in the hatchling, especially in the critical stage of first feeding, is of great importance for rearing techniques of turtles. In the present study, the developments of intestinal histomorphology and microbiota during the first 30 days (0, 10, 20 and 30 days after hatched) of Chinese strip-necked turtle (Mauremys sinensis) were investigated. The results showed that the height and width of intestinal villus and total length of intestine progressed with turtle's growth. The diversity of intestinal microbiota (Shannon and Simpson index) was no significant difference between first 30 days, but the richness indexes (Chao and Ace) significantly increased at 20 days after hatched. The phylum Firmicutes, Proteobacteria and Bacteroidetes dominated the turtle gut microbiota. The abundances of family Weeksellaceae, Aeromonadaceae, Cytophagaceae and Lachnospiraceae increased, whereas the family Ruminococcaceae decreased at 10 days after the first feeding. With turtle growing, the abundances of Bacteroidaceae and Methylobacteriaceae increased, which dominated at 30 days (28.49% and 22.08%, respectively). The order of Clostridiales and genus of Clostridium dominated in all the tested turtle samples in spite of the low abundance of environment including vermiculite, water and feed. Therefore, the members of Clostridium would be potential probiotic for turtles although future investigations should determine their roles in the turtle gut microbiota.

Biodegradation and disintegration of expanded polystyrene by land snails Achatina fulica

Despite increasing evidence of widespread plastic pollution in soil, it remains largely unknown about the fate of plastic influenced by soil animals. In this study, ingestion and biodegradation capability of expanded polystyrene (PS) foam was investigated in a globally distributed soil invertebrate, Achatina fulica. After 4-week exposure, 18.5 ± 2.9 mg polystyrene was ingested per snail, and egested microplastics (1.343 ± 0.625 mm) in feces with significant mass loss of mean 30.7%. Gel permeation chromatography analysis indicated a significant increase in weight-average molecular weight (Mw) and number-average molecular weight (Mn) of feces-residual PS, indicating limited extent depolymerization. Fourier transform infrared spectroscopy and proton nuclear magnetic resonance confirmed the formation of functional groups of oxidized intermediates. Suppression of gut microbes with oxytetracycline did not affect the depolymerization, indicating the independence of gut microbes. High-throughput sequencing analysis revealed significant shifts in the gut microbiome after ingestion of PS, with an increase of family Enterobacteriaceae, Sphingobacteriaceae, and Aeromonadaceae, suggesting that gut microorganisms were associated with PS biodegradation. These findings suggest that plastic litter can be disintegrated into microplastics and partially biodegraded by A. fulica, which highlights the significance of soil animals for the fate of plastic and its biodegradation in soil environments.

The duodenal microbiome is altered in small intestinal bacterial overgrowth.

Small intestinal bacterial overgrowth (SIBO) is highly prevalent and is associated with numerous gastrointestinal disorders, but the microbes involved remain poorly defined. Moreover, existing studies of microbiome alterations in SIBO have utilized stool samples, which are not representative of the entire gastrointestinal tract. Therefore, we aimed to determine and compare the duodenal microbiome composition in SIBO and non-SIBO subjects, using duodenal aspirates from subjects undergoing standard-of-care esophagogastroduodenoscopy without colon preparation. Using the recently-redefined cutoff for SIBO of >103 colony forming units per milliliter (CFU/mL), 42 SIBO and 98 non-SIBO subjects were identified. Duodenal samples from SIBO subjects had 4x103-fold higher counts than non-SIBO subjects when plated on MacConkey agar (P<0.0001), and 3.8-fold higher counts when plated on blood agar (P<0.0001). Twenty subjects had also undergone lactulose hydrogen breath tests (LHBTs), of whom 7/20 had SIBO. At the 90-minute timepoint, 4/7 SIBO subjects had positive LHBTs (rise in hydrogen (H2) ≥ 20 ppm above baseline), as compared to 2/13 non-SIBO subjects. 16S ribosomal RNA (rRNA) sequencing revealed that SIBO subjects had 4.31-fold higher relative abundance of Proteobacteria (FDR P<0.0001) and 1.64-fold lower Firmicutes (P<0.0003) than non-SIBO subjects. This increased relative abundance of Proteobacteria correlated with decreased α-diversity in SIBO subjects (Spearman R = 0.4866, P<0.0001) Specific increases in class Gammaproteobacteria correlated with the area-under-the-curve for H2 for 0–90 mins during LHBT (R = 0.630, P = 0.002). Increases in Gammaproteobacteria resulted primarily from higher relative abundances of the family Enterobacteriaceae (FDR P<0.0001), which correlated with the symptom of bloating (Spearman R = 0.185, 2-tailed P = 0.028). Increases in family Aeromonadaceae correlated with urgency with bowel movement (Spearman R = 0.186, 2-tailed P = 0.028). These results validate the >103 CFU/mL cutoff for the definition of SIBO, and also reveal specific overgrowth of Proteobacteria in SIBO vs. non-SIBO subjects, coupled with an altered Proteobacterial profile that correlates with symptom severity. Future research may elucidate host-microbiome interactions underlying these symptoms in SIBO patients.

Urinary tract infection due to Aeromonas species: An uncommon causative agent

BackgroundMembers of the genus Aeromonas are Gram-negative bacilli, belonging to family Aeromonadaceae, and are widely found in various aquatic environments. The most common species associated with human infections are A. hydrophila, A. caviae, and A. veronii biovar sobria. Aeromonas species are recognized as emerging opportunistic pathogens in humans mainly causing gastrointestinal infections and wound infections with or without progression to septicaemia. Aeromonas organisms rarely cause urinary tract infection (UTI) and are not known uropathogens. CaseWe report a series of UTI due to Aeromonas species in three adult patients, specifically identified as A. veronii biovar sobria in two patients and A. hydrophila in one patient. Two patients had history of occupational exposure to aquatic environment. ConclusionsThe cases highlight another expanded range of infections caused by Aeromonas spp. that can be encountered in a community setting and indicate that infections with Aeromonas spp. should be kept in mind while investigating for the etiology of UTI, especially in adult patients with occupational exposure to aquatic ecosystems.

Spatial structure of the microbiome in the gut of Pomacea canaliculata

BackgroundGut microbes can contribute to their hosts in food digestion, nutrient absorption, and inhibiting the growth of pathogens. However, only limited studies have focused on the gut microbiota of freshwater snails. Pomacea canaliculata is considered one of the worst invasive alien species in the world. Elucidating the diversity and composition of the microbiota in the gut of P. canaliculata snails may be helpful for better understanding the widespread invasion of this snail species. In this study, the buccal masses, stomachs, and intestines were isolated from seven P. canaliculata snails. The diversity and composition of the microbiota in the three gut sections were then investigated based on high-throughput Illumina sequencing targeting the V3-V4 regions of the 16S rRNA gene.ResultsThe diversity of the microbiota was highest in the intestine but lowest in the buccal mass. A total of 29 phyla and 111 genera of bacteria were identified in all of the samples. In general, Ochrobactrum, a genus of putative cellulose-degrading bacteria, was the most abundant (overall relative abundance: 13.6%), followed by Sediminibacterium (9.7%), Desulfovibrio (7.8%), an unclassified genus in the family Aeromonadaceae (5.4%), and Cloacibacterium (5.4%). The composition of the microbiota was diverse among the different gut sections. Ochrobactrum (relative abundance: 23.15% ± 7.92%) and Sediminibacterium (16.95 ± 5.70%) were most abundant in the stomach, an unclassified genus in the family Porphyromonadaceae (14.28 ± 7.29%) and Leptotrichia (8.70 ± 4.46%) were highest in the buccal mass, and two genera in the families Aeromonadaceae (7.55 ± 4.53%) and Mollicutes (13.47 ± 13.03%) were highest in the intestine.ConclusionsThe diversity and composition of the microbiome vary among different gut sections of P. canaliculata snails. Putative cellulose-degrading bacteria are enriched in the gut of P. canaliculata.

Dongshaea marina gen. nov., sp. nov., a facultatively anaerobic marine bacterium that ferments glucose with gas production.

Two isolates of heterotrophic, facultatively anaerobic, marine bacteria, designated DM1 and DM2T, were recovered from a lagoon sediment sample of Dongsha Island, Taiwan. Cells were Gram-reaction-negative rods. Nearly all of the cells were non-motile and non-flagellated during the late exponential to early stationary phase of growth, while a few of the cells exhibited motility with monotrichous flagellation. The two isolates required NaCl for growth and grew optimally at about 30 °C, 2-3 % NaCl and pH 7-8. They grew aerobically and could achieve anaerobic growth by fermenting d-glucose or other carbohydrates with production of acids and the gases, including CO2 and H2. Ubiquinone Q-8 was the only respiratory quinone. Cellular fatty acids were predominated by C16 : 0, C18 : 1ω7c and C16 : 1ω7c. The major polar lipid was phosphatidylethanolamine. Strains DM1 and DM2T had DNA G+C contents of 52.0 and 51.8 mol%, respectively, as determined by HPLC analysis. Phylogenetic analyses based on 16S rRNA gene sequences clearly indicated that the two isolates formed a distinct genus-level lineage in the family Aeromonadaceae of the class Gammaproteobacteria and was an outgroup with respect to a stable supragenic clade comprising species of the genera Oceanimonas, Oceanisphaera and Zobellella. The phylogenetic data and those from chemotaxonomic, physiological and morphological characterizations support the establishment of a novel species and genus inside the family Aeromonadaceae, for which the name Dongshaea marina gen. nov., sp. nov. is proposed. The type strain is DM2T (=BCRC 81069T=JCM 32096T).

Biochemical but not compositional recovery of skin mucosal microbiome communities after disruption.

BackgroundThe microbiomes of animals are complex communities that strongly affect the health of the hosts. Microbiomes on mucosal surfaces have the highest densities and most extensive biochemical exchanges with the hosts. Although antibiotics are potent tools to manage infections, they can disrupt the normal microbiota, causing numerous side effects.Materials and methodsTaking a community ecology approach, mucosal microbiome community responses to five disruptive conditions (two broad-spectrum antibiotics, a biocide, elevated temperature, and rinsing) were analyzed. Skin of the fish Gambusia affinis was the mucosal model. Microbiome recovery was measured by culturable counts, community biochemical profiles, genetic fingerprinting, and community 16S gene sequencing (rinsing condition only).ResultsFollowing all disruptions, the total counts rose and then returned to the pre-treatment (PT) level. This overgrowth was confirmed via direct staining and community metabolic activity measurements. After rinsing, diversity decreased and one taxon dominated (family Aeromonadaceae) temporarily, the findings similar to numerous other studies with antibiotics. While the community did not return to the PT taxonomic composition, the biochemical profile did.ConclusionThis suggests that the biochemical pathways in a community are important during recovery, and a return to the original composition is not required to restore original function.

Hemorrhagic blisters in fulminant Aeromonas hydrophila bacteremia: Case report and literature review

The Aeromonas species, belonging to the family Aeromonadaceae, are opportunistic pathogens found in humans with an incidence rate of 76 cases per million inhabitants in Southern Taiwan. The incidence of Aeromonas septicemia is relatively low, accounting for less than 15% of cases. Patients diagnosed with Aeromonas hydrophila bacteremia who were presented with skin blisters and septic shock have been reported to have a mortality rate of 100%. Aeromonas infection must be considered in the differential diagnosis of gangrene-like tissue damage or skin lesions in patients with end-stage renal disease, due to the potential sources of infections. A 49-year-old Taiwanese diabetic woman with end-stage renal disease had underwent regular hemodialysis. She was referred to our hospital due to a one-day course of fever, dyspnea, hypotension, and fulminant hemorrhagic blisters covering her whole body. A physical examination uncovered multiple hemorrhagic blisters, along with a ruptured blister over the lower left leg. Laboratory tests revealed an elevation of liver enzymes, impaired renal function, lactatemia, and high anion-gap metabolic acidosis. Cultures of both blood and hemorrhagic blister fluid grew Aeromonas hydrophila. However, she experienced persistent shock despite aggressive intravenous fluid, empiric antibiotics, and inotropic agents with norepinephrine and dopamine. Early diagnosis and prompt management using intravenous fluids, antibiotics and surgical debridement is recommended in order to improve a patient’s survival rate.

The role of gut microbiome and its interaction with arsenic exposure in carotid intima-media thickness in a Bangladesh population

BackgroundEmerging data suggest that inorganic arsenic exposure and gut microbiome are associated with the risk of cardiovascular disease. The gut microbiome may modify disease risk associated with arsenic exposure. Our aim was to examine the inter-relationships between arsenic exposure, the gut microbiome, and carotid intima-media thickness (IMT)—a surrogate marker for atherosclerosis. MethodsWe recruited 250 participants from the Health Effects of Arsenic Longitudinal Study in Bangladesh, measured IMT and collected fecal samples in year 2015–2016. 16S rRNA gene sequencing was conducted on microbial DNA extracted from the fecal samples. Arsenic exposure was measured using data on arsenic concentration in drinking water wells over time to derive a time-weighted water arsenic index. Multivariable linear regression models were used to test the inter-relationships between arsenic exposure, relative abundance of selected bacterial taxa from phylum to genus levels, and IMT. ResultsWe identified nominally significant associations between arsenic exposure, measured using either time-weighted water arsenic or urinary arsenic, and the relative abundances of several bacterial taxa from the phylum Tenericutes, Proteobacteria, and Firmicutes. However, none of the associations retained significance after correction for multiple testing. The relative abundances of the family Aeromonadaceae and genus Citrobacter were significantly associated with IMT after correction for multiple testing (P-value = 0.02 and 0.03, respectively). Every 1% increase in the relative abundance of Aeromonadaceae and Citrobacter was related to an 18.2-μm (95% CI: 7.8, 28.5) and 97.3-μm (95% CI: 42.3, 152.3) difference in IMT, respectively. These two taxa were also the only selected family and genus using the LASSO variable selection method. There was a significant interaction between Citrobacter and time-weighted water arsenic in IMT (P for interaction = 0.04). ConclusionsOur findings suggest a role of Citrobacter in the development of atherosclerosis, especially among individuals with higher levels of arsenic exposure.

Zobellella endophytica sp. nov., isolated from the roots of Phragmites communis in the Kumtag Desert.

A Gram-negative, aerobic, non-spore-forming, rod-shaped, motile bacterium, named strain 59N8T, was isolated from Phragmites communis roots in the Kumtag Desert. Phylogenetic analysis based on the 16S rRNA gene sequence showed that the isolate belongs to the genus Zobellella within the family Aeromonadaceae. The analysis showed that strain 59N8T was most closely related to Zobellella taiwanensis ZT1T. The average nucleotide identity value with Zobellella taiwanensis ZT1T was 88.2 %, and the digital DNA-DNA hybridization value was 29.7±2.4 %, which was calculated using the Genome-to-Genome Distance Calculator. The G+C content of strain 59N8T was 62.8 mol%. Strain 59N8T grew at 0-5 % (w/v) NaCl (optimum, 0-4 %), pH 6.0-9.0 (optimum, 7.0-8.0) and at 10-45 °C. The major cellular fatty acids were summed feature 8 (C18 : 1ω7c/C18 : 1ω6c), summed feature 3 (C16 : 1ω7c/C16 : 1ω6c) and C16 : 0. The major polar lipids in strain 59N8T were phosphatidylethanolamine and phosphatidylglycerol. Based on the chemotaxonomic, phylogenetic and phenotypic data, strain 59N8T represents a novel species in the genus Zobellella, for which the name Zobellellaendophytica sp. nov. is proposed. The type strain is 59N8T (=ACCC 60074T=KCTC 62456T).

Pseudaeromonas paramecii sp. nov., isolated from the ciliate Paramecium caudatum and emendation of the genus Pseudaeromonas

A Gram-stain-negative, oxidase-negative and catalase-negative, motile, rod-shaped bacterial strain, designated PCS8T, hosted by the ciliate Paramecium caudatum was investigated by using a polyphasic approach. Strain PCS8T was observed to be able to grow at 12-44 °C (optimum, 36-37 °C), at pH 6.0-10.0 (optimum, 7.0) and in the presence of 0-3 % NaCl (optimum, 1-2 %). It could hydrolyse starch and aesculin and produce acid from d-sorbitol, myo-inositol, glycerol and l-rhamnose. The sequence similarity of the new isolate was 96.9 % with respect to Pseudaeromonas pectinilytica and 96.3 % with respect to Pseudaeromonas sharmana. Phylogenetically, strain PCS8T falls within the cluster comprising the Pseudaeromonas species. The predominant cellular fatty acids of strain PCS8T were C16 : 0 (35.8 %), summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c; 35.1 %) and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c; 10.8 %). This novel strain also contained various fatty acids that are not detected in other members of the genus Pseudaeromonas, such as C16 : 0 3-OH, C18 : 1ω9c and summed feature 5 (C18 : 2ω6,9c and/or C18 : 0 ante). Strain PCS8T contained ubiquinone-8 as the sole respiratory quinone and phosphatidylethanolamine and phosphatidylglycerol as major polar lipids. The G+C content of the genomic DNA of the type strain was 66.5 mol%. Based on the distinct phenotypic, phylogenetic, chemotaxonomic and G+C content results, strain PCS8T represents a currently undescribed species within the genus Pseudaeromonas in the family Aeromonadaceae, for which we suggest the name Pseudaeromonas paramecii sp. nov. with the type strain PCS8T (=KCTC 62038T=JCM 32226T). An emended description of the genus Pseudaeromonas is also provided.

Identification and characterization of chitinolytic bacteria isolated from a freshwater lake.

To develop a novel type of biocontrol agent, we focus on bacteria that are characterized by both chitinase activity and biofilm development. Chitinolytic bacteria were isolated from sediments and chitin flakes immersed in the water of a sand dune lake, Sakata, in Niigata, Japan. Thirty-one isolates from more than 5100 isolated strains were examined chitinase activity and biofilm formation. Phylogenetic analysis of these isolates based on the 16S rRNA gene sequences revealed that most isolates belonged to the family Aeromonadaceae, followed by Paenibacillaceae, Enterobacteriaceae, and Neisseriaceae. The specific activity of chitinase of four selected strains was higher than that of a reference strain. The molecular size of one chitinase produced by Andreprevotia was greater than that of typical bacterial chitinases. The dialyzed culture supernatant containing chitinases of the four strains suppressed hyphal growth of Trichoderma reesei. These results indicate that these four strains are good candidates for biocontrol agents.

Intestinal microbiota of healthy and unhealthy Atlantic salmon Salmo salar L. in a recirculating aquaculture system

The present study sampled the intestinal content of healthy and unhealthy Atlantic salmon (Salmo salar L.), the ambient water of unhealthy fish, and the biofilter material in the recirculating aquaculture system (RAS) to understand differences in the intestinal microbiota. The V4-V5 regions of the prokaryotic 16S rRNA genes in the samples were analyzed by MiSeq high-throughput sequencing. The fish were adults with no differences in body length or weight. Representative members of the intestinal microbiota were identified. The intestinal microbiota of the healthy fish included Proteobacteria (44.33%), Actinobacteria (17.89%), Bacteroidetes (15.25%), and Firmicutes (9.11%), among which the families Micrococcaceae and Oxalobacteraceae and genera Sphingomonas, Streptomyces, Pedobacter, Janthinobacterium, Burkholderia, and Balneimonas were most abundant. Proteobacteria (70.46%), Bacteroidetes (7.59%), and Firmicutes (7.55%) dominated the microbiota of unhealthy fish, and Chloroflexi (2.71%), and Aliivibrio and Vibrio as well as genera in the family Aeromonadaceae were most strongly represented. Overall, the intestinal hindgut microbiota differed between healthy and unhealthy fish. This study offers a useful tool for monitoring the health status of fish and for screening the utility of probiotics by studying the intestinal microbiota.

Reclassification of Aeromonas sharmana to a new genus as Pseudaeromonas sharmana gen. nov., comb. nov., and description of Pseudaeromonas pectinilytica sp. nov. isolated from a freshwater stream.

A Gram-reaction-negative, rod-shaped, facultatively anaerobic, motile bacterium, designated strain AR1T, was isolated from a freshwater stream in Jeonju, South Korea. Strain AR1T showed highest 16S rRNA gene sequence similarity (96.83 %) and also formed a separate clade with Aeromonas sharmana GPTSA-6T in the phylogenetic tree reconstructed among the members of the family Aeromonadaceae. Major cellular fatty acids are summed feature 3 (C16 : 1ω7c/C16 : 1ω6c) and C16: 0. Diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol are the predominant polar lipids. The genomic DNA G+C content was found to be 54.7 mol%. However, earlier studies on 16S rRNA gene, gyrB, rpoD and universal target region of cpn60 sequences of the members of the genus Aeromonas recommended the transfer of Aeromonas sharmana to a new genus. Hence, based on the comparative polyphasic data obtained during the present study and also on the previous recommendations, it is proposed that Aeromonas sharmana be transferred to a novel genus as Pseudaeromonas sharmana gen. nov., comb. nov. with strain GPTSA-6T (=DSM 17445T=MTCC 7090T=CIP 109378T=CCUG 54939T) as the type strain of the type species of the genus. Also, it is proposed that strain AR1T be designated as a representative of a novel species of this new genus, namely Pseudaeromonas pectinilytica sp. nov. The type strain is AR1T (=KCTC 42754T=JCM 31503T).