Intensive industrial and urban growth has led to the release of increasing amounts of environmental pollutants. Contamination by metals, in particular, deserves special attention due to their toxicity and potential to bioaccumulate via the food chain. Conventional techniques for the removal of toxic metals, radionuclides and precious metals from wastewater all have a number of drawbacks, such as incomplete metal extraction, high cost and risk of generating hazardous by‐products. Biosorption is a cost‐effective and environment‐friendly technology, an alternative to conventional wastewater treatment methods. Biosorption is a metabolically independent process, in which dead microbial biomass is capable of removal and concentrating metal ions from aqueous solutions. Free microbial biosorbents are of small size and low density, insufficient mechanical stability and low elasticity, which causes problems with metal ion desorption, separation of the sorbent from the medium and its regeneration. Hence, the possibilities for the implementation of continuous biosorbent processes for metal removal in flow‐type reactor systems are reduced and the practical application of biosorption in industrial conditions is limited. By immobilizing microbial biomass on suitable carriers the disadvantages of free biosorbents are eliminated and more opportunities for practical use of biosorption become available. This review examines different immobilization techniques and carriers, certain basic features and possibilities of using immobilized microbial biosorbents for the removal and concentration of metals from aqueous solutions.

The aim of the present study was to investigate biofilm-forming capabilities of clinically isolated strains Escherichia coli, associated with different urinary tract infections. Biofilm production was detected in 36% of the isolates from UTI. Additionally some of virulence factors are estimated to find correlation between antibiotic resistance, hemolysins, morfotypes and biofilm production. Our data indicate that no combination of VFs was highly associated with biofilm production.

Microorganisms inhabiting freshwater environments are an integral part of the aquatic ecosystems. Very few data are available regarding the profiles of the microbial communities in the reservoirs in Bulgaria, despite their key role in the biogeochemical processes. In the present study, we provide the first comprehensive metagenomic analysis on the planktonic bacterial diversity of two large and economically important Bulgarian reservoirs (Batak and Tsankov Kamak) using next-generation sequencing of 16S ribosomal RNA gene (16S rRNA). Analysis of the metagenomic amplicon datasets, including quality filtering, clustering of Operational Taxonomic Units and taxonomy assignment revealed that 78.45% of the microbial communities between the two reservoirs were overlapping. The diversity (H) and Pielou's evenness (J) indices declined along the longitudinal axis of both reservoirs. The estimated values for the Shannon diversity index are typically observed in oligotrophic lakes. The microbial communities of both reservoirs were dominated by Proteobacteria, followed by Actinobacteria and Bacteroidetes all comprised over 95% of the relative abundance, regardless of the reservoir's large hydrogeological differences. The bacterioplankton was characterized by high phylogenetic heterogeneity in the taxonomic structure, being distributed among 211 genera. The genera Limnohabitans and Rhodoferax held the absolute predominance, implying their significance in the aquatic food webs. The obtained data can contribute to the better systematic understanding of the microbial diversity of freshwater environments.

Waste biomass from Bacillus cereus immobilized in sodium alginate and co-immobilized with activated carbon or with bentonite into alginate gel was studied for Pb(II), Cd(II) and Hg(II) removal from aqueous solutions. The composite biosorbent consisting of waste B. cereus biomass co-immobilized with activated carbon into alginate beads was selected as the most prospective for heavy metals removal. Immobilization increased both the removal capacity and the mechanical strength of the biosorbent. Major process parameters were optimized and maximum removal efficiency of 92.13% was reached for Pb(II) ions at pH 5.0, biosorbent dosage 2 g/L, temperature 25 C, agitation speed 120 rpm for 120 min.

Current knowledge on antimicrobial susceptibility pattern of uropathogens is necessary for appropriate therapy. The objective of this study was to investigate antibiotic susceptibility of 28 clinically isolated strains Escherichia coli, associated with different urinary tract infections. Lowest susceptibility detected was for betalactams ampicillin and ampicillin/sulbactam. High susceptibility was detected for aminoglycoside antibiotics. Approximately half of investigated strain showed multidrug resistance profiles. Plasmid content of E. coli isolates was investigated and participation of detected plasmids in drug resistance was discussed. Our data show the high level of antimicrobial resistance and extended spectrum b-lactamases (ESBL) production amongst the uropathogens causing urinary tract infection.