The microbial diversity of the intestinal tract content of the river trout from two Lithuanian rivers has been investigated by molecular methods: polymerase chain reaction amplification and sequencing of partial 16S rRNA genes. Predominant bacterial populations detected in the river trout intestinal tract from the Skroblus River were Rahnella (21%), from the Xeimena River, Aeromonas (41.7%) and Plesiomonas (22.9%). Buttiauxella agrestis, Budvicia aquatica, Erwinia persicinus, Yersinia mollaretii, Y. kristensenii, Y. rohdei, Moellerella wisconsensis, Obesumbacterium proteus, Pantoea cedenensis, Rahnella aquatilis, and Rahnella sp. from the Enterobacteriaceae family have been detected in the intestinal tract of freshwater salmonid fish for the first time.KEY WORDS: 16S rRNA gene sequencing, intestinal microbiota, river trout.

The microbial diversity of culturable intestinal microflora of wild freshwater salmonid fishes salmon Salmo salar and sea trout Salmo trutta trutta juveniles (0+ years old) from the same environmental conditions were investigated by means of molecular identification techniques and analysis of diet. Significant differences in the intestinal microbial diversity were observed in different fish species. The predominant group in the intestinal tract of the salmon comprised representatives of the Enterobacteriaceae family (23%), Plesiomonas (19.2%) and Carnobacterium (15.3%). Predominant microbiota in sea trout intestinal tract were Enterobacteriaceae (52%), Aeromonas (22%) and Pseudomonas (14%). The results show that Enterobacteriaceae were predominant in the intestinal tract of the salmon and the sea trout juveniles raised on diets of different compositions. However, molecular identification of the intestinal microbiota at the species or genus level revealed differences in these fish species. Bacteria in the hindgut of salmon included Pragia and Serratia. However, bacteria in the gut contents of sea trout from the Enterobacteriaceae family were Buttiauxella, Enterobacter, Moellerella, Pantoea, Rahnella and Tiedjeia arctica. A novel phylotype of T. arctica is harbored in the intestinal tract of wild salmon, and may correspond to a previously undescribed species.

Erwinia typographi sp. nov., isolated from bark beetle (Ips typographus) gut

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A b s t r a c tThe infection of Lithuanian honey bee colonies by Nosema apis and N. ceranae and the consequences were analysed over a four-year (2011 -2014) period. Both mono-infection either by N. apis or N. ceranae, and co-infection by both Nosema species, were found. There was a decrease in the percentage of Nosema infected colonies during the four-year study period. There were fewer colonies infected by N. ceranae, whereas the number of colonies with N. apis remained approximately at the same level during the study. The prevalence of both types of Nosema in honey bee colonies varied seasonally, i.e. there was a higher percentage of colonies infected in spring and summer but very rarely was Nosema detected in autumn. Mono-infection by N. apis, and co-infection by both Nosema species, were significantly more often recorded in weak and moderate colonies than in strong colonies. Mono-infection by N. ceranae was more often detected in weak colonies than in moderate and strong colonies, but more often detected in strong than in moderate colonies. A moderate link between a high prevalence of N. ceranae infection and an increased risk for winter colony mortality was observed.

Abstract:The investigation was carried out to ascertain the cause of mass mortalities in European perch (Perca fluviatilis L.) in NorthLithuanian rivers in 2008 that reached a maximum in mid-autumn at a water temperature of 6ºC. Marked changes were detected in morphophysiological parameters (spleen-, gill-, liver-and heart-somatic indices), which corresponded to changes in haematological parameters (leukocyte count was significantly elevated or reduced) of the infected fish. The viable bacterial counts in the gill, liver and kidney of infected live fish samples ranged from 2.3±0.3 x 10 3 to 6.3±0.4 x 10 3 c.f.u./g. The BOX-PCR fingerprinting technique was used for characterization and identification of the isolated bacterial strains from liver and kidney of infected perch. The bacterial isolates were identified by sequence analysis of the 16S rRNA gene. Pathogenic Aeromonas salmonicida subsp. salmonicida has been identified as a possible causative agent of the observed mortality in European perch.

For research, two differently polluted lakes were selected: Lake Dringis, Aukðtaitija National Park, as an ecosystem pattern of a weak anthropogenic influence, and Lake Drûkðiai, as a regularly polluted water body. Lake Drûkðiai, the cooling basin of Ignalina Nuclear Power Plant, through its tributaries is being polluted with industrial and municipal sewage. Samples were taken from four differently polluted mouths of tributaries: the mouth of the Rièanka Stream; the mouth of the Gulbinës Stream affected by urban rain sewerage of Visaginas (URS-2); the mouth of the Gulbinëlë Stream into which municipal sewage of Visaginas (MS) and industrial rain sewerage from INPP (IRS-1.2) flow. The work was aimed to determine the role of the symbiotic bacterioflora of the roach digestive tract in protein decomposition, as well as the dependence of proteolytic enzyme activity upon environmental pollution. Comparison of the proteolytic activity (PA) of the roach intestinal bacterioflora showed reliable differences between Lakes Dringis and Drûkðiai. The total mean PA of bacterioflora in Lake Dringis roach intestines was established to be twice higher than that in Drûkðiai. At the URS-2, MS, and IRS-1.2 mouths of Lake Drûkðiai, the mean PAs of the isolates were reliably similar. The mean PA was a little higher in the Rièankas mouth roach intestinal bacteria. The highest mean PA in active strains as well as the highest total mean PA was typical of Lake Dringis roach intestinal strains. In Lake Dringis, the highest mean PA in active bacteria strains was determined in the IRS-1.2 mouth roach intestines. The research revealed the enzyme activity in fish intestinal bacterioflora to be dependent upon the ecology state of environment.

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