A novel ascosporogenous yeast species,Zygosaccharomyces siamensis,and the sugar tolerant yeasts associated with raw honey collected in Thailand

Diversity of yeasts in association with bees and their food sources has been explored during the last decade.In Thailand,there has been no study of yeast identification in honey and bees.Hence,a total of 186 yeast strains were isolated from 37 honey samples of 12 different bee species.On the basis of morphological and physiological characteristics,55 representative strains were chosen and identified by sequence analysis of the 26S rDNA D1/D2 domain and the ITS region.The data were compared with the published sequences and the results showed the occurrence of 19 ascomycetous and 1 basidiomycetous yeast species.Six strains of the new species were isolated.Phylogenetic analysis of the 26S rDNA D1/D2 sequence revealed that they were conspecific and most closely related to Zygosaccharomyces mellis.Based on the ITS sequence,the new species was clustered with the type"and clearly distinguished from the type!.Sequence analysis of combined ITS-26S rDNA D1/D2 showed similar results.The occurrence of these two types,with a divergence of more than 1%in their sequences,and low DNA relatedness among them suggested that members of the typeβcan be regarded as separate species.An analysis of the morphological and physiological characteristics was performed.Ascospore formation was observed on acetate agar and Gorodkowa agar.The new Zygosaccharomyces species differed physiologically from Z.mellis in 4 assimilation tests.This data supports the hypothesis that the new species,Zygosaccharomyces siamensis,is a novel ascosporogenous yeast.The type strain is JCM 16825T(=CBS 12273T)and a description is given here.

Comparative susceptibility and immune responses of Asian and European honey bees to the American foulbrood pathogen, Paenibacillus larvae

American foulbrood (AFB) disease is caused by Paenibacillus larvae. Currently, this pathogen is widespread in the European honey bee— Apis mellifera. However, little is known about infectivity and pathogenicity of P. lan'ae in the Asiatic cavity-nesting honey bees, Apis cerana. Moreover, comparative knowledge of P. larvae infectivity and pathogenicity between both honey bee species is scarce. In this study, we examined susceptibility, larval mortality, survival rate and expression of genes encoding antimicrobial peptides (AMPs) including defensin, apidaecin, abaecin, and hymenoptaecin in A. mellifera and A. cerana when infected with P. larvae. Our results showed similar effects of P. larvae on the survival rate and patterns of AMP gene expression in both honey bee species when bee larvae are infected with spores at the median lethal concentration (LC5 0 ) for A. mellifera. All AMPs of infected bee larvae showed significant upregulation compared with noninfected bee larvae in both honey bee species. However, larvae of A. cerana were more susceptible than A. mellifera when the same larval ages and spore concentration of P. larvae were used. It also appears that A. cerana showed higher levels of AMP expression than A. mellifera. This research provides the first evidence of survival rate, LC50 and immune response profiles of Asian honey bees, A. cerana, when infected by P. larvae in comparison with the European honey bee, A. mellifera.

Midgut bacterial communities in the giant Asian honeybee （Apis dorsata） across 4 developmental stages： A comparative study

Bacterial communities are known to play important roles during the developmental stages of insects, but current knowledge of bacteria associated with the midgut of Apis dorsata, the giant Asian honeybee, is limited. Using polymerase chain reaction-denaturing gradient gel electrophoresis analysis （PCR-DGGE） and 16S rRNA sequencing, the aim of this study was to determine the dynamics of bacterial community structure across four A. dorsata life stages in different geographical locations. The results reveal that bacterial diversity increased as the bee progressed through larval stage to newly emerged worker and old worker. However, in the pupal stage, no bands identified as bacteria could be observed. Overall, 2 bacterial phyla （Proteobacteria and Firmicutes） and 4 classes （Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Bacilli） were identified, but the frequency varied among the different stages and locations. The classes of Gammaproteobacteria and Bacilli dominated among larval, newly emerged worker and old worker developmental stages.