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Background Air pollution has been a serious health issue in Beijing for years. Airborne antibiotic-resistant bacteria could be a potential health crisis as reserve of antibiotic resistance transmission in environment. The composition and antibiotic resistance pattern of culturable bacterial community and how these are affected by air pollution remain unclear. Objectives This study aimed to compare the compositions and antibiotic resistance patterns of culturable bacteria in polluted and non-polluted weather conditions in Beijing. Methods Air samples were collected indoors and outdoors during polluted and non-polluted weather using six-stage Andersen Samplers. For each isolated bacterium, the 16S ribosomal RNA gene was amplified, sequenced, and blasted against the National Center for Biotechnology Information database Antibiotic resistance was conducted by antimicrobial susceptibility testing. Results Bacterial concentration in polluted weather was significantly higher than in non-polluted weather, both indoors and outdoors (P, Highlights • Bacterial concentration was significantly higher in polluted weather. • Multidrug-resistant bacteria occupied approximately one fourth of bacteria in both weathers. • Gram-negative bacteria had greater abundance in polluted weather. • Multidrug-resistance was more severe in gram-negative bacteria. • Penicillins was resisted by over 70% culturable airborne bacteria.

North Sinai deserts were surveyed for the predominant plant cover and for the culturable bacteria nesting their roots and shoots. Among 43 plant species reported, 13 are perennial (e.g. Fagonia spp., Pancratium spp.) and 30 annuals (e.g. Bromus spp., Erodium spp.). Eleven species possessed rhizo-sheath, e.g. Cyperus capitatus, Panicum turgidum and Trisetaria koelerioides. Microbiological analyses demonstrated: the great diversity and richness of associated culturable bacteria, in particular nitrogen-fixing bacteria (diazotrophs); the majority of bacterial residents were of true and/or putative diazotrophic nature; the bacterial populations followed an increasing density gradient towards the root surfaces; sizeable populations were able to reside inside the root (endorhizosphere) and shoot (endophyllosphere) tissues. Three hundred bacterial isolates were secured from studied spheres. The majority of nitrogen-fixing bacilli isolates belonged to Bacillus megaterium, Bacillus pumilus, Bacillus polymexa, Bacillus macerans, Bacillus circulans and Bacillus licheniformis. The family Enterobacteriaceae represented by Enterobacter agglomerans, Enterobacter sackazakii, Enterobacter cloacae, Serratia adorifera, Serratia liquefaciens and Klebsiella oxytoca. The non-Enterobacteriaceae population was rich in Pantoae spp., Agrobacterium rdiobacter, Pseudomonas vesicularis, Pseudomonas putida, Stenotrophomonas maltophilia, Ochrobactrum anthropi, Sphingomonas paucimobilis and Chrysemonas luteola. Gluconacetobacter diazotrophicus were reported inside root and shoot tissues of a number of tested plants. The dense bacterial populations reported speak well to the very possible significant role played by the endophytic bacterial populations in the survival, in respect of nutrition and health, of existing plants. Such groups of diazotrophs are good candidates, as bio-preparates, to support the growth of future field crops grown in deserts of north Sinai and irrigated by the water of El-Salam canal.

A tool based on cellular fatty acids of culturable heterotrophic bacterioplankton was developed in order to characterize and differentiate northern Adriatic, particularly oligotrophic high-salinity, waters. Variances in growing abilities and population dominance of particle-attached and free-living bacteria cultured in three media, Marine Broth, diluted Marine Broth (1:10) and R2 broth were used. Three groups of water layers were distinguished by Hierarchical clustering analysis: eutrophic, oligotrophic and oligotrophic nutrient-selected. Significance of the difference between resulting groups was tested by two-way ANOVA (with replication). Eutrophic layers were characterized by readily culturable particle attached and free-living fractions of the bacterial community in all three media, all dominated by fast-growing γ -Proteobacteria. In contrast, low productive, oligotrophic water layers were characterized by much weaker culturability, different population dominance of the free-living community in respect to attached counterpart or even growth arrest in response to all media. The free-living bacteria from “ strictly” oligotrophic environments demonstrated minimum culturability in Marine Broth while that from selective oligotrophic environment were culturable and dominated either by Cytophaga-Flavobacter complex, α -Proteobacteria or γ -Proteobacteria. The conclusive evidence on selective and refractory nature of organic compounds in these waters bears the dominant culturability of Cytophaga-Flavobacter complex and α -Proteobacteria in free-living communities in all growth-media. Response in fatty acid dominance ratios significantly depends on trophic state and fraction (p < 0.05) although the effect of trophic state is completely different in attached and free fraction. In both fractions, tested separately, a significant influence of trophic state was present (p < 0.05), while effect of media on fatty acid response was insignificant (p > 0.05). A certain interaction between media and trophic status was present in attached fraction (p < 0.05), yet in free fraction it was not observed (p > 0.05), meaning that any systematic difference between trophic states is the same for each media tested. Accordingly, the free-living fraction of bacterioplankton is more informative attribute and can be used solely as an indicator of the water layer trophic condition.

The toxic effect of chromate on soil microbial communities is not well documented, although microorganisms control biogeochemical cycling, contribute to formation of soil structure, regulate the fate of organic matter applied to soil. In this study the effects of short- and middle-term chromate on the soil microbial community were investigated. The shifts in the size and in the diversity of culturable heterotrophic bacterial community, the resistance to Cr(VI) of heterotrophic bacteria, the presence of cyanobacteria, the activity of 19 enzymes, and the ATP content were monitored over time (120 days) in soil microcosms artificially contaminated with three concentrations of chromate (50, 250 and 1000 mg kg−1 soil). The chromate contamination affected the structure and the diversity of the soil bacterial community. Bacterial strains isolated from the microcosm contaminated with the highest concentration of chromate were identified by 16S rDNA gene sequencing. All isolates belonged to the genus Pseudomonas, were able to reduce Cr(VI), and showed a high resistance to chromate. To our knowledge, this is the first report that shows Pseudomonas strains having the capability to resist up to 40 mM of Cr(VI) on minimal medium. The cyanobacterial group was more sensitive to chromate contamination than culturable heterotrophic bacteria. No cyanobacterial growth was detected in enrichment cultures from the soil polluted with the highest chromate concentration. Some enzymes were inhibited by high concentrations of chromate, whereas others were stimulated. The ATP content in microcosms was strongly affected by chromate. We conclude that the soil microbial community responds to chromate pollution through changes in community structure, in metabolic activity, and in selection for Cr(VI)-resistance.