Association between intestinal microbiome and inflammatory bowel disease: Insights from bibliometric analysis.

The gut microbiome is highly linked to inflammatory bowel disease (IBD). A total of 3890 publications related to the two terms from 2000 to 2020 were extracted from the Web of Science Core Collection to study the association from a bibliometric perspective. Publications on this topic have grown rapidly since 2008. The United States and Harvard University are the country and institution with the largest number of publications, respectively. Inflammatory Bowel Diseases is the most productive journal with 211 published articles. The most influential journal in this field is Gut with 13,359 citations. The co-citation analysis of references showed that the IBD-related topics with the highest focus are "gut microbiota," "metagenomics," "bacterial community," "fecal microbiota transplantation," "probiotics," and "colitis-associated colorectal cancer." Keyword cluster and keyword burst analyses showed that "gut microbiota," "metagenomics," and "fecal microbiota transplantation" are currently the most researched topics in the field of IBD. The literature in this field is mainly distributed between alterations of the intestinal microbiota, microbial metabolites, and related host signaling pathways. Probiotic treatment also frequently appears in literature. This bibliometric analysis can guide future research and promote the development of the field of gut microbiome and IBD.

Outer membrane protein OmpU is related to iron balance in Vibrio alginolyticus.

Outer membrane protein U (OmpU) is a major porin from Vibrio alginolyticus and has been considered a vaccine candidate against infection by V. alginolyticus. After pre-incubated with polyclonal antibody against rOmpU, V. alginolyticus showed a 78% decrease in extracellular iron level, suggesting that interruption of OmpU could increase intracellular iron level. The mRNA expression of ompU under iron-limited conditions was determined using real-time reverse transcriptase PCR. The mRNA level of ompU was downregulated to 0.27-, 0.036- and 0.019-fold after the addition of the iron chelator 2,2'-bipyridyl for 10, 30 and 60 min, respectively. In addition, the promoter of ompU contained a ferric uptake regulator (Fur) binding site, which revealed the potential regulation of ompU by Fur and iron. Fur from V. alginolyticus was purified and used for electrophoretic mobility shift assay. The result showed that in the absence of Fe2+, purified recombinant Fur could specifically bind to the promoter DNA of ompU, while in the presence of Fe2+, the binding of Fur and the promoter DNA was suppressed. Our study preliminarily explored the function of OmpU in iron balance in V. alginolyticus, and these findings were helpful in understanding iron metabolism in V. alginolyticus.

Isolation and characterization of a virulence related Vibrio alginolyticus strain Wz11 pathogenic to cuttlefish, Sepia pharaonis.

Vibrio alginolyticus is a ubiquitous marine opportunistic pathogen that can infect various hosts in marine environment. In the present study, V. alginolyticus strain Wz11 was isolated from diseased cuttlefish, Sepia pharaonis, with 20% of promoted death and high survival capacity in skin mucus and tissue liquid. Its growth, siderophore production, and expressions of haemolysin and swarming related genes were characterized under iron limited conditions. The minimal inhibitory concentration (MIC) of 2,2'-dipyridyl (DP) to V. alginolyticus strain Wz11 was 640 µM. While growth of V. alginolyticus strain Wz11 was inhibited by DP, production of iron-seizing substances, haemolytic activity and swarming motility were increased. Moreover, expressions of haemolysin related genes tlh, tdh and vah and flagellar related genes flgH, fliC, fliD and fliS were also characterized using real-time reverse transcriptase PCR. Expression of tdh was up-regulated to 7.7-fold, while expressions of tlh and vah were down-regulated to 0.016-fold and 0.03-fold, respectively. The expression of fliC, flgH, fliD and fliS was up-regulated to 4.9-, 3.8-, 8.6- and 4.5-fold, respectively. Concluded from our results suggested that V. alginolyticus strain Wz11 was considered as a potential pathogen of S. pharaonis, and iron level played an important role in the production of iron-seizing substances, and activities of haemolysin and bacterial swarming as well as their related gene expressions.

Characteristics of the iron uptake-related process of a pathogenic Vibrio splendidus strain associated with massive mortalities of the sea cucumber Apostichopus japonicus.

Under low iron bioavailability environment, many bacteria acquire iron for growth and survival through siderophore-mediated iron acquisition systems. However, until now, little research on the growth, siderophore production and siderophore receptors of Vibrio splendidus Vs under iron limited conditions has been reported. In our present study, V. splendidus Vs could survive in media supplemented with 160 µM 2,2'-dipyridyl (DIP), but 74.5% of the growth was suppressed at 48 h, while the siderophore production of V. splendidus Vs increased by 35.9%. As the OD600 of V. splendidus Vs decreased when the concentration of DIP was increased from 40 to 80 µM, the siderophore production of V. splendidus Vs increased from 34.0% to 43.4% at 24 h, and it was further determined to be a hydroxamate siderophore. To explore the potential siderophore receptors anchored on the outer membrane of V. splendidus Vs, outer membrane proteins from cells grown with and without 80 µM DIP were extracted and the differentially expressed proteins were identified by SDS-PAGE and MALDI-TOF/TOF MS. Five proteins, aerobactin siderophore receptor IutA, enterobactin receptor protein FepA, ATP synthase subunit A, ATP synthase subunit B and the ATP synthase F0F1 subunit beta were identified. Real-time reverse transcriptase PCR showed that mRNA levels of iutA, fepA, atpA, atpB and atpß-F0F1 were upregulated 271.5-, 15.1-, 1.1-, 2.5- and 67.9-fold respectively, after 6 h in cells treated with 80 µM DIP. In addition, the promoters of the siderophore receptor genes of iutA and fepA had apparent ferric uptake regulator (Fur) binding sites. Combined with the simultaneous production of both the hydroxamate siderophore and its corresponding aerobactin siderophore receptor IutA, these results suggested that there might be a hydroxamate siderophore-IutA mediated iron uptake pathway in V. splendidus Vs.