Dynamic changes in the structure of microbial communities in Baltic Sea coastal seawater microcosms modified by crude oil,shale oil or diesel fuel

The coastal waters of the Baltic Sea are constantly threatened by oil spills, due to the extensive transportation of oil products across the sea. To characterise the hydrocarbon-degrading bacterial community of this marine area, microcosm experiments on diesel fuel, crude oil and shale oil were performed. Analysis of these microcosms, using alkane monooxygenase (alkB) and 16S rRNA marker genes in PCR-DGGE experiments, demonstrated that substrate type and concentration strongly influence species composition and the occurrence of alkB genes in respective oil degrading bacterial communities. Gammaproteobacteria (particularly the genus Pseudomonas) and Alphaproteobacteria were dominant in all microcosms treated with oils. All alkB genes carried by bacterial isolates (40 strains), and 8 of the 11 major DGGE bands from the microcosms, had more than 95% sequence identity with the alkB genes of Pseudomonas fluorescens. However, the closest relatives of the majority of sequences (54 sequences from 79) of the alkB gene library from initially collected seawater DNA were Actinobacteria. alkB gene expression, induced by hexadecane, was recorded in isolated bacterial strains. Thus, complementary culture dependent and independent methods provided a more accurate picture about the complex seawater microbial communities of the Baltic Sea.     

Crosstalk between growth and somatic maintenance in young animals

Growing animals face allocation problems whenever receiving suboptimal amounts of resources in very stochastic natural environments, possibly through a trade‐off between growth and somatic maintenance. However, the extent to which such a trade‐off exists has remained an open question. We used an insulin‐like growth factor 1 (IGF‐1) injection treatment in free‐living pied flycatcher Ficedula hypoleuca nestlings to see how IGF‐1 levels mediate the development of an antioxidant phenotype via glutathione peroxidase (GPx). Our study showed that IGF‐1 levels underlie variation in GPx activity and provides important information for understanding the mechanisms behind the growth variation of passerines.     

Survival and catabolic performance of introduced Pseudomonas strains during phytoremediation and bioaugmentation field experiment

A long-term field experiment was carried out to estimate the efficiency of bioaugmentation in combination with phytoremediation for oil shale chemical industry solid waste dump area remediation. Soil samples for microbiological and chemical analysis were collected during 3 years after bacterial biomass application. Microbial communities in soil samples were analysed using both culture-based and molecular methods. The survival of the introduced bacterial strains was confirmed by cultivation-based Box-PCR genomic fingerprints and denaturing gradient gel electrophoresis fingerprinting of the 16S rRNA and lmPH genes. The introduced bacterial strains as well as corresponding catabolic genes were recovered several years after biomass application, predominantly from the rhizosphere of birches. Soil samples from bioaugmented plots showed an elevated potential for degradation of phenolic compounds even 40 months after treatment. Based on our results we can conclude that the introduced Pseudomonas strains both survived, and their metabolic traits have persisted at the contaminated site over a long period of time.     

Insulin‐like growth factor 1 relieves the constraints on the growth of young wild passerines

To gain a selective advantage for survival in stochastic environments, the growth of different body parameters of juvenile animals should be constantly adjusted according to prevailing conditions. Hormones, especially insulin‐like growth factor 1 (IGF‐1), are an important part of physiological mechanisms mediating life‐history variability in free‐living animals when connecting available resources (e.g. food) with pathways of somatic growth. We used an IGF‐1 injection treatment in free‐living European Pied Flycatcher Ficedula hypoleuca nestlings to mimic experimentally the differentiation of growth conditions for chicks with a similar genetic background. We showed that there is probably a physiological trade‐off for young animals between the growth rates of structural size and body mass, where IGF‐1 could be part of the physiological modulatory system of this trade‐off. By weakening internal constraints that limit growth, IGF‐1 could help to relieve the trade‐off between these competing body size parameters.     

Experimental study of the effect of preen oil against feather bacteria in passerine birds

Avian plumage harbors various pathogens such as feather-degrading bacteria, which have the potential to reduce host fitness. A growing body of evidence suggests that the secretion of the uropygial gland of birds—preen oil—acts as one of the first lines of defence against harmful bacteria. However, previous studies on the antimicrobial impact of preen oil have yielded controversial results. The impact of preen oil on bacterial densities of feathers was experimentally investigated in two passerine species: great tits Parus major and pied flycatchers Ficedula hypoleuca. More specifically, we tested whether the antibacterial effect of the preen oil secreted by the same individual differs from that of the preen oil originating from the gland of other species. In the laboratory, ventral feathers were treated with preen oil from (1) an individual’s own gland, (2) from the gland of another passerine species, or (3) from the gland of a phylogenetically distant bird species. We detected a significant antibacterial effect of preen oil on bacteria that were attached to feathers, though the effect did not depend on whether the oil originated from the individual’s own gland or from the gland of another bird species. However, treatment with preen oil suppressed the density of bacteria more in the pied flycatcher than in the great tit. This is the first study providing experimental evidence that preen oil represents an important antimicrobial mechanism against those plumage bacteria that are attached to feathers.