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SummaryIn this study, prevalence, biotechnological and safety profi les of 588 Enterococcus isolates isolated from raw milk and Istrian cheese during diff erent stages of ripening were analyzed. Despite the low and variable presence of enterococci in milk ((3.65±2.93) log CFU/mL), highly comparable enterococcal populations were established aft er 30 days of cheese ripening ((7.96±0.80) log CFU/g), confi rming Enterococcus spp. as a major part of the core microbiota of Istrian cheese. The dominant species were E. faecium (53.8 %) and E. faecalis (42.4 %), while minor groups, consisting of E. durans (2.84 %) and E. casselifl avus (0.95 %), also occurred. A pronounced intraspecies variability was noticed based on molecular fi ngerprinting, with 35 strains (genotypes) detected. Most of the genotypes were farm-specifi c with one third being shared between the farms. This genotype variability refl ected particular diff erences of Istrian cheese production, mainly variable salt concentration, ripening temperature and air humidity as well as microclimatic or vegetation conditions. There was considerable variation between the strains of the same species regarding wide range of biotechnologically important traits as well as their ability to survive in simulated gastrointestinal conditions. A considerable number of strains were resistant to critically important antibiotics such as tetracycline (43.56 %), erythromycin (35.79 %) and vancomycin (23.48 %). Polymerase chain reaction-based detection did not identify any of the common genetic determinants for vancomycin and erythromycin resistance; for tetracycline tetM gene was detected. The presence of virulence genes including agg, efaAfs, gelE, cylM, cylB, cylA, esp, efaAfm, cob and cpd was frequently recorded, especially among E. faecalis strains.

Nutrient turnover in soils is strongly driven by soil properties, including clay mineral composition. One main nutrient is phosphorus (P), which is known to be easily immobilized in soil. Therefore, the specific surface characteristics of clay minerals might substantially influence P availability in soil and thus the microbial strategies for accessing P pools. We used a metagenomic approach to analyze the microbial potential to access P after 842 days of incubation in artificial soils with a clay mineral composition of either non-expandable illite (IL) or expandable montmorillonite (MT), which differ in their surface characteristics like soil surface area and surface charge. Our data indicate that microorganisms of the two soils developed different strategies to overcome P depletion, resulting in similar total P concentrations. Genes predicted to encode inorganic pyrophosphatase (ppa), exopolyphosphatase (ppx), and the pstSCAB transport system were higher in MT, suggesting effective P uptake and the use of internal poly-P stores. Genes predicted to encode enzymes involved in organic P turnover like alkaline phosphatases (phoA, phoD) and glycerophosphoryl diester phosphodiesterase were detected in both soils in comparable numbers. In addition, Po concentrations did not differ significantly. Most identified genes were assigned to microbial lineages generally abundant in agricultural fields, but some were assigned to lineages known to include oligotrophic specialists, such as Bacillaceae and Microchaetaceae.

The incidence of antibiotic resistance in pathogenic bacteria has become an alarming clinical and social problem. Therefore, the demand for alternative antimicrobial compounds has increased. In this study, a chemical profile of honey bee (Apis mellifera L.) venom (HBV) has been determined by HPLC and FTIR-ATR spectroscopy, and tested for antibacterial activity, as well as efficiency with regard to conventional antibiotics. The investigated HBV was of high quality with melittin and total protein contents of 70.10 ± 7.01%, and 84.44 ± 3.12 g/100 g, respectively. The purity of HBV was confirmed by FTIR-ATR spectral profiling, which revealed a unique pattern of absorption bands that are characteristic of its major fractions. In addition, HBV showed a broad spectrum of activity against all three tested biomasses of potentially pathogenic Gram-positive and Gram-negative bacteria with MIC values ranging between 12.5 and 200 µg/mL, and MBC between 12.5 and 400 µg/mL. When compared to conventional antibiotics, HBV (400 µg) showed up to 27.8% efficiency of tetracycline (30 µg), 52.2% erythromycin (15 µg), 21.2% ciprofloxacin (5 µg), and 34.6% of ampicillin-sulbactam (20 µg). The overall results demonstrate the therapeutic potential of the analyzed HBV.