Süheyla Karataş

Multilocus Sequence Analysis of Close Relatives Vibrio anguillarum and Vibrio ordalii

ABSTRACT The genetic heterogeneity of the close relatives Vibrio anguillarum and Vibrio ordalii, both serious pathogens of fish causing extensive losses in aquaculture, was studied. Eight housekeeping genes, i.e., atpA, ftsZ, gapA, gyrB, mreB, rpoA, topA, and pyrH, were partially sequenced in 116 isolates from diverse fish species and geographical areas. The eight genes appear to be under purifying selection, and the genetic diversity in the total data set was estimated to be 0.767 ± 0.026. Our multilocus sequence analysis (MLSA) scheme identified several widespread clonal complexes and resolved the isolates, for the most part, according to serotype. Serotype O2b isolates from diseased cod in Norway, Ireland, and Scotland were found to be extremely homogeneous. Horizontal gene transfer appears to be fairly common within and between clonal complexes. Taken together, MLSA and in silico DNA-DNA hybridization (DDH) calculations suggest that some isolates previously characterized as V. ordalii, i.e., 12B09, FF93, FS144, and FS238, are in fact V. anguillarum isolates. The precise taxonomic situation for two isolates from Atlantic cod that display several traits consistent with V. ordalii, i.e., NVI 5286 and NVI 5918, and a single environmental strain that was previously considered to represent V. ordalii, i.e., FF167, is less clear. IMPORTANCE It is still being debated whether V. anguillarum and V. ordalii represent separate bacterial species. Our study addresses this issue and elucidates the degree of genetic variability within this group of closely related bacteria, based on a substantial number of isolates. Our results clearly illustrate the existence of different populations among putative V. ordalii isolates. On the basis of additional full-length genomic analysis, we conclude that most environmental isolates previously identified as V. ordalii lie firmly within the species V. anguillarum. While bona fide fish-pathogenic V. ordalii isolates display a very close genetic relationship with V. anguillarum, they combine a clearly divergent evolutionary pattern with clear phenotypic differences. The study also highlights the need for further characterization of fish-pathogenic isolates from the northern Atlantic region that share phenotypic characteristics with V. ordalii but are genetically closer to V. anguillarum. The retention of taxonomic distinctions between the phenotypically different groups of bacteria is of practical advantage to microbial ecologists and veterinarians.

Bir Deniz Akvaryumunda Salpa Balıklarında (Sarpa salpa) V. harveyi’nin Neden Olduğu İlk Vibriozis Olgusu

Bu calisma, bir deniz akvaryumundan alinan hasta salpa baliklarinda ( Sarpa salpa ) hastaliga neden olan etken veya etkenleri tanimlamak uzere yapilmistir. Hasta baliklarin vucudunda hafif siddette deri renginde acilma ile birlikte pul kayiplari gozlenmistir. Ic bakida, karaciger ve bagirsak dokularinin hiperemik ve kas dokusunun da hemorajik oldugu tespit edilmistir. Doku kesitleri histopatolojik olarak incelendiginde, enfeksiyonun; ozellikle solungac epitelyumu, bagirsak mukozasi, kalp kasi ve dalagin hematopoetik dokusunu etkiledigi belirlenmistir. Fenotipik ve biyokimyasal ozellikleri ve SSU rRNA dizileme sonuclarina gore; incelenen tum ic organlardan (bobrek, dalak, karaciger) ve kan dokusundan Vibrio harveyi bakterisi izole edilmistir. Buna ek olarak, incelenen baliklardan sadece birinin kan dokusundan ve dalagindan alinan orneklerde Vibrio vulnificus ve Pseudoalteromonas piscicida bakterileri de izole edilmistir.