Differences in culturable microbial communities in bird nestboxes according to orientation and influences on offspring quality in great tits (Parus major).

Although bird-microbial interactions have become a topic of increasing research, the influence of nest-site characteristics, such as cavity orientation, on nest microbial communities in free-living passerines has not, to our knowledge, been investigated. This is despite the possibility of microbial differences explaining non-random patterns in nest-site selection and offspring quality, such as those exhibited by great tits (Parus major). We swabbed great tit nestboxes that faced either south-southwest (180-269°) or north-northeast (0-89°). Overall, 28 bacterial species and 11 fungal species were isolated, but the culturable microbial community differed substantially between different orientations-indeed nestboxes could be classified to their orientation group with high accuracy using microbial data. Nestboxes facing south-southwest had a significantly higher fungal load (typically double) than those facing north-northeast due to a higher abundance of two species, Epicoccum purpurascens and Cladosporium cladosporioides. There was no relationship between total bacterial load and orientation, although the abundance of one species, Pseudomonas veronii, was significantly lower in south-southwest boxes. The abundance of the allergen E. purpurascens explained almost 20% of the variation in offspring quality, being significantly and inversely related to chick size (high loads associated with small, poor quality, chicks). Our results provide empirical evidence for a correlation between nestbox orientation and culturable microbial load and a further correlation between abundance of one species, E. purpurascens, and offspring quality. Thus, microbial load, which is itself influenced by nest cavity parameters, could be the proximate factor that influences nest-site choice through its effect on offspring quality (and thus, overall fecundity).

Intraspecific variation and interspecific differences in the bacterial and fungal assemblages of blue tit (Cyanistes caeruleus) and great tit (Parus major) nests.

Although interest in the relationship between birds and microorganisms is increasing, few studies have compared nest microbial assemblages in wild passerines to determine variation within and between species. Culturing microorganisms from blue tit (Cyanistes caeruleus) and great tit (Parus major) nests from the same study site demonstrated diverse microbial communities with 32 bacterial and 13 fungal species being isolated. Dominant bacteria were Pseudomonas fluorescens, Pseudomonas putida, and Staphylococcus hyicus. Also common in the nests were the keratinolytic bacteria Pseudomonas stutzeri and Bacillus subtilis. Dominant fungi were Cladosporium herbarum and Epicoccum purpurascens. Aspergillus flavous, Microsporum gallinae, and Candida albicans (causative agents of avian aspergillosis, favus, and candidiasis, respectively) were present in 30%, 25%, and 10% of nests, respectively. Although there were no differences in nest mass or materials, bacterial (but not fungal) loads were significantly higher in blue tit nests. Microbial species also differed interspecifically. As regards potential pathogens, the prevalence of Enterobacter cloacae was higher in blue tit nests, while Pseudomonas aeruginosa-present in 30% of blue tit nests-was absent from great tit nests. The allergenic fungus Cladosporium cladosporioides was both more prevalent and abundant in great tit nests. Using discriminant function analysis (DFA), nests were classified to avian species with 100% accuracy using the complete microbial community. Partial DFA models were created using a reduced number of variables and compared using Akaike's information criterion on the basis of model fit and parsimony. The best models classified unknown nests with 72.5-95% accuracy using a small subset of microbes (n = 1-8), which always included Pseudomonas agarici. This suggests that despite substantial intraspecific variation in nest microflora, there are significant interspecific differences-both in terms of individual microbes and the overall microbial community-even when host species are closely related, ecologically similar, sympatric, and construct very similar nests.

Isolation and characterization of Acidicaldus organivorus, gen. nov., sp. nov.: a novel sulfur-oxidizing, ferric iron-reducing thermo-acidophilic heterotrophic Proteobacterium.

Thermo-acidophilic prokaryotes isolated from geothermal sites in Yellowstone National Park were identified as novel alpha-Proteobacteria, distantly related (approximately 93% 16S rRNA gene identity) to the mesophilic acidophile Acidisphaera rubrifaciens. One of these isolates (Y008) was shown to be more thermophilic than all previously characterized acidophilic proteobacteria, with a temperature optimum for growth between 50 and 55 degrees C and a temperature maximum of 65 degrees C. Growth was observed in media maintained at pH between 1.75 and 3.0 and was fastest at pH between 2.5 and 3.0. The G + C content of Y008 was 71.8+/-0.9 mol%. The acidophile was able to grow heterotrophically on a range of organic substrates, including various monosaccharides, alcohols and amino acids and phenol, though growth on single organic compounds required the provision of one or more growth factors. The isolate oxidized sulfur to sulfuric acid in media containing yeast extract, but was not capable of autotrophic growth with sulfur as energy source. Growth occurred under aerobic conditions and also in the absence of oxygen via anaerobic respiration using ferric iron as terminal electron acceptor. Based on these genotypic and phenotypic traits, it is proposed that Y008 represents the type species of Acidicaldus organivorus, gen. nov., sp. nov.