Population Dynamics of Vibrio and Pseudomonas Species Isolated from Farmed Tasmanian Atlantic Salmon (Salmo salar L.): A Seasonal Study

Abstract

Vibrio and Pseudomonas species have been shown to be part of the normal microbiota of Atlantic salmon (Salmo salar L.), with some strains causing disease in fish. The factors affecting their prevalence and persistence in the salmon gut, however, have not been well studied. In this study, we collected 340 Vibrio and 150 Pseudomonas isolates from the hindgut of farmed Tasmanian Atlantic salmon, fed with two commercially available diets. Samples were collected every 6-8 weeks between July 2011 and May 2012. Isolates from selective agar were initially identified using biochemical tests and confirmed using genus-specific primers and 16S ribosomal RNA (16S rRNA) sequencing. Random amplified polymorphic DNA (RAPD) PCR was used to type both Pseudomonas and Vibrio; the latter was further typed using a biochemical fingerprinting method (PhP-RV plates). We observed low species diversity with strains comprising Vibrio ichthyoenteri/Vibrio scophthalmi, Vibrio crassostreae/Vibrio splendidus, Aliivibrio finisterrensis, Photobacterium phosphoreum and Pseudomonas fragi. Out of 340 Vibrio isolates, 238 (70 %) belonged to 21 clonal types and were found predominantly during summer when water temperatures reached 15 to 21 °C. Of these, the four major clonal types were found in multiple samples (70 %). P. fragi, on the other hand, was only found during the colder water temperatures and belonged to 18 clonal types. The presence of both groups of bacteria and their clonal types were independent of the fish diets used, suggesting that the water temperature was the main factor of the prevalence and persistence of these bacteria in the gut of Atlantic salmon.

The environmental and host‐associated bacterial microbiota of Arctic seawater‐farmed Atlantic salmon with ulcerative disorders

“…The higher abundance of Vibrio in September might be a function of elevated seawater temperature. This observation is consistent with previous studies showing that Vibrio abundance is positively correlated with temperature in the intestinal tract of Atlantic salmon (Green, Smullen & Barnes 2013;Hatje et al 2014;Zarkasi et al 2014), and on external surfaces of other fish species (Tao et al 2012;Larsen et al 2015). Although in low abundance, M. viscosa-like sequences are present in all ulcer samples, which is in agreement with the many culturebased investigations of winter-ulcers that have resulted in the identification of mixed cultures of mainly Aliivibrio and Vibrio spp.…”

“…This observation is consistent with previous studies showing that Vibrio abundance is positively correlated with temperature in the intestinal tract of Atlantic salmon (Green, Smullen & Barnes ; Hatje et al . ; Zarkasi et al . ), and on external surfaces of other fish species (Tao et al .…”

Temporal fluctuation in the abundance of alginate‐degrading bacteria in the gut of abalone H aliotis gigantea over 1 year

“…It is likely that water temperature is the main abiotic factor affecting variation. Its effect on gut microbiota composition of healthy salmon (especially Vibrio and Pseudoalteromonas ) has been documented (Hatje, Neuman, Stevenson, Bowman & Katouli ). Vibrios are among the most common group of gut bacteria in marine vertebrates and invertebrates (Thompson, Iida & Swings ; Preheim, Boucher, Wildschutte, David, Veneziano, Alm & Polz ).…”

Differential Response of Digesta- and Mucosa-Associated Intestinal Microbiota to Dietary Black Soldier Fly (Hermetia illucens) Larvae Meal in Seawater Phase Atlantic Salmon (Salmo salar)

“…Notably, Pseudomonas has also been isolated from intestinal digesta and mucosa of Atlantic salmon by traditional culturing approaches (71,(88)(89)(90), and reported as a member of Atlantic salmon core microbiota in culture-independent studies (19, 23, 33, 34, 38, 91). Due to the low taxonomic resolution of amplicon sequencing, it is difficult to discern contaminat-ing taxa from true signals solely based on taxonomic labels.…”