Vibrios of some deep-water invertebrates

Characterization of the intestinal microbiota of the sea cucumber Holothuria glaberrima

High-throughput 16S rRNA gene sequencing has been used to identify the intestinal microbiota of many animal species, but that of marine invertebrate organisms remains largely unknown. There are only a few high-throughput sequencing studies on the intestinal microbiota of echinoderms (non-vertebrate Deuterostomes). Here we describe the intestinal microbiota of the sea cucumber Holothuria glaberrima, an echinoderm, well-known for its remarkable power of regeneration. We characterized the microbiota from the anterior descending intestine, the medial intestine (these two comprise the small intestine) and the posterior descending intestine (or large intestine), using pyrosequencing to sequence the V4 region of the 16S rRNA gene. We compared animals in their natural marine environment and in sea-water aquaria. A total of 8,172 OTU's were grouped in 10 bacterial phyla, 23 classes, 44 orders, 83 families, 127 genera and 1 group of unknown bacteria, present across the digestive tract of 10 specimens. The results showed that the anterior intestine is dominated by Proteobacteria (61%) and Bacteroidetes (22%), the medium intestine is similar but with lower Bacteroidetes (4%), and the posterior intestine was remarkably different, dominated by Firmicutes (48%) and Bacteroidetes (35%). The structure of the community changed in animals kept in aquaria, which had a general dominance of Firmicutes and Bacteroidetes, regardless the intestinal segment. Our results evidence that in the natural sea environment, there is intestinal segment differentiation in the microbiota of H. glaberrima, which is lost in artificial conditions. This is relevant for physiological studies, such as mechanisms of digestive regeneration, which might be affected by the microbiota.

Phylogenetic diversity and axial distribution of microbes in the intestinal tract of the polychaete Neanthes glandicincta

The phylogenetic diversity and axial distribution of microorganisms in three sections of the gastrointestinal tracts of the polychaete Neanthes glandicincta was evaluated using both most probable number method and cloning analyses of 16S rRNA genes in this study. Quantification of the density of microorganisms in the gut showed that aerobic microorganisms decreased from anterior to posterior, while anaerobic ones showed a reverse trend. The total numbers of microorganisms decreased significantly (p < 0.05, analysis of variance) but more rapidly from the anterior to the middle segment. Phylogenetic analysis showed that the dominating phylogenetic groups included Methanomicrobiales I: Methanosaetaceae (up to 66% of archaeal clones), delta-Proteobacteria (up to 42% of bacterial clones), and gamma-Proteobacteria (up to 30% of bacterial clones) widely distributed throughout the entire gut. Other microbiota distributed in different gut sections were Methanomicrobiales II: Methanospirillaceae, Methanomicrobiales III, Thermoplasmatales, Crenarchaea, Methanobacteriaceae, and Methanosarcinales for archaea; and alpha-Proteobacteria, beta-Proteobacteria, Fusobacteria, Clostridia, Chloroflexi, and Planctomycetes for bacteria. The results reveal a difference in microbial community structure along the gut of N. glandicincta. The various phylogenetic diversity and axial distribution of microbes along the gut might indicate an environmental gradient from anterior to posterior sections affecting the structure of the microbial community.

Identification of Vibrio splendidus as a Member of the Planktonic Luminous Bacteria from the Persian Gulf and Kuwait Region with luxA Probes

Hybridization probes specific for the luxA genes of four groups of luminous bacteria were used to screen luminous isolates obtained from the Persian Gulf, near Al Khiran, Kuwait Nine of these isolates were identified as Vibrio harveyi , a commonly encountered planktonic isolate, while three others showed no hybridization to any of the four probes ( V. harveyi, Vibrio fischeri, Photobacterium phosphoreum , or Photobacterium leiognathi ) under high-stringency conditions. Polymerase chain reaction amplification was used to prepare a luxA probe against one of these isolates, K-1, and this probe was screened under high-stringency conditions against a collection of DNAs from luminous bacteria; it was found to hybridize specifically to the DNA of the species Vibrio splendidus . A probe prepared against the type strain of V. splendidus (ATCC 33369) was tested against the collection of luminous bacterial DNA preparations and against the Kuwait isolates and was found to hybridize only against the type strain and the three unidentified Kuwait isolates. Extensive taxonomic analysis by standard methods confirmed the identification of the 13 isolates.

The human pathogenic vibrios--a public health update with environmental perspectives

Pathogenic Vibrio species are naturally-occurring bacteria in freshwater and saline aquatic environments. Counts of free-living bacteria in water are generally less than required to induce disease. Increases in number of organisms towards an infective dose can occur as water temperatures rise seasonally followed by growth and concentration of bacteria on higher animals, such as chitinous plankton, or accumulation by shellfish and seafood. Pathogenic Vibrio species must elaborate a series of virulence factors to elicit disease in humans. Activities which predispose diarrhoeal and extraintestinal infections include ingestion of seafood and shellfish and occupational or recreational exposure to natural aquatic environments, especially those above 20 degrees C. Travel to areas endemic for diseases due to pathogenic Vibrio species may be associated with infections. Host risk factors strongly associated with infections are lack of gastric acid and liver disorders. Involvement of pathogenic Vibrio species in cases of diarrhoea should be suspected especially if infection is associated with ingestion of seafood or shellfish, raw or undercooked, in the previous 72 h. Vibrio species should be suspected in any acute infection associated with wounds sustained or exposed in the marine or estuarine environment. Laboratories serving coastal areas where infection due to pathogenic Vibrio species are most likely to occur should consider routine use of TCBS agar and other detection regimens for culture of Vibrio species from faeces, blood and samples from wound and ear infections.