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The taxonomic status of strain P5891T, isolated from an Adélie penguin beak swab, was investigated. Based on the 16S rRNA gene sequence, the strain was identified as a potentially novel Corynebacterium species, with the highest sequence similarities to Corynebacterium rouxii FRC0190T (96.7%) and Corynebacterium epidermidicanis DSM 45586T (96.6%). The average nucleotide identity values between strain P5891T and C. rouxii FRC0190T and C. epidermidicanis DSM 45586T were 68.2 and 69.2%, respectively. The digital DNA–DNA hybridization values between strain P5891T and C. rouxii FRC0190T and C. epidermidicanis DSM 45586T were 23.7 and 21.4%, respectively. Phylogenetic trees based on the 16S rRNA sequence placed strain P5891T in a separate branch with Corynebacterium canis 1170T and Corynebacterium freiburgense 1045T, while a phylogenomic tree based on the Corynebacterium species core genome placed the strain next to Corynebacterium choanae 200CHT. Extensive phenotyping and genomic analyses clearly confirmed that strain P5891T represents a novel species of the genus Corynebacterium, for which the name Corynebacterium mendelii sp. nov. is proposed, with the type strain P5891T (=CCM 8862T=LMG 31627T).

A group of 11 bacterial strains was isolated from streams and lakes located in a deglaciated northern part of James Ross Island, Antarctica. They were rod-shaped, Gram-stain-negative, motile, and catalase-positive and produced blue-violet-pigmented colonies on R2A agar. A polyphasic taxonomic approach based on 16S rRNA gene sequencing, whole-genome sequencing, automated ribotyping, repetitive element sequence-based PCR (rep-PCR), MALDI-TOF MS, fatty acid profile, chemotaxonomy analyses, and extensive biotyping was applied in order to clarify the taxonomic position of these isolates. Phylogenetic analysis based on the 16S rRNA gene indicated that all the isolates constituted a coherent group belonging to the genus Rugamonas. The closest relatives to the representative isolate P5900T were Rugamonas rubra CCM 3730T, Rugamonas rivuli FT103WT, and Rugamonas aquatica FT29WT, exhibiting 99.2%, 99.1%, and 98.6% 16S rRNA pairwise similarity, respectively. The average nucleotide identity and digital DNA-DNA hybridization values calculated from the whole-genome sequencing data clearly proved that P5900T represents a distinct Rugamonas species. The G+C content of genomic DNAs was 66.1mol%. The major components in fatty acid profiles were summed feature 3 (C16:1 7c/C16:1 6c), C 16:0, and C12:0. The cellular quinone content contained exclusively ubiquinone Q-8. The predominant polar lipids were diphosphatidylglycerol, phosphatidylglycerol, and phosphatidylethanolamine. The polyamine pattern was composed of putrescine, 2-hydroxputrescine, and spermidine.

Despite unfavourable Antarctic conditions, such as cold temperatures, freeze-thaw cycles, high ultraviolet radiation, dryness and lack of nutrients, microorganisms were able to adapt and surprisingly thrive in this environment. In this study, eight cold-adapted Flavobacterium strains isolated from a remote Antarctic island, James Ross Island, were studied using polyphasic taxonomic approach to determine their taxonomic position. Phylogenomic analyses based on 16S rRNA gene and 92 core genes clearly showed that these strains formed two distinct phylogenetic clusters comprising three and five strains, with average nucleotide identities significantly below 90 % in between both proposed species as well as between their closest phylogenetic relatives. Phenotyping revealed a unique pattern of biochemical and physiological characteristics enabling differentiation from the closest phylogenetically related Flavobacterium spp. Chemotaxonomic analyses showed that type strains P4023T and P7388T were characterized by the major polyamine sym-homospermidine and a quinone system containing predominantly menaquinone MK-6. In the polar lipid profile phosphatidylethanolamine, an ornithine lipid and two unidentified lipids lacking a functional group were detected as major lipids. These characteristics along with fatty acid profiles confirmed, that these species belong to the genus Flavobacterium. Thorough genomic analysis revealed presence of numerous cold-inducible or cold-adaptation associated genes, such as cold-shock proteins, proteorhodopsin, carotenoid biosynthetic genes or oxidative-stress response genes. Genomes of type strains surprisingly harboured multiple prophages, with many of them predicted to be active. Genome-mining identified biosynthetic clusters in type strain genomes with majority not matching any known biosynthetic genes which indicates further research possibilities involving these psychrotrophic bacteria. Antibiotic susceptibility testing revealed multidrug-resi

Pragia fontium is one of the few species that belongs to the group of atypical hydrogen sulfide-producing enterobacteria. Unlike other members of this closely related group, P. fontium is not associated with any known host and has been reported as a free-living bacterium. Whole genome sequencing and metabolic fingerprinting confirmed the phylogenetic position of P. fontium inside the group of atypical H2S producers. Genomic data have revealed that P. fontium 24613 has limited pathogenic potential, although there are signs of genome decay. Although the lack of specific virulence factors and no association with a host species suggest a free-living style, the signs of genome decay suggest a process of adaptation to an as-yet-unknown host.

Cílem práce bylo popsat vývoj obsahu vybraných biogenních aminů (histaminu, tyraminu, putrescinu a kadaverinu) ve 4 vrstvách eidamského sýru v závislosti na 3 režimech zrání/skladování v průběhu 98 dnů. Pro analýzu biogenních aminů byla použita iontově-výměnná chromatografie. Dalším cílem bylo identifikovat mikrobiální původce biogenních aminů v analyzovaném materiálu. Pro identifikaci izolovaných bakterií byly použity fenotypové znaky a PCR fingerprinting. Nejvyšší obsahy tyraminu, putrescinu a kadaverinu byly zjišťovány u sýrů uchovávaných po celou dobu sledování ve zracím sklepě při 10°C. Nižší obsahy biogenních aminů byly zjišťovány u vzorků, které byly po 38 dnech ve zracím sklepě (10°C) přesunuty do chladírenského zařízení (5°C). Nejnižší koncentrace biogenních aminů byly detekovány u sýrů, které byly po 23 dnech ve zracím sklepě (10°C) přesunuty do chladírenského zařízení (5°C). Histamin nebyl v průběhu 98 dnů ani u jednoho režimu detekován. Jako hlavní původci testovaných biogenních aminů v analyzovaných sýrech byli detekováni non-starterové bakterie mléčného kvašení Lactobacillus curvatus subsp. curvatus, komplex Lactobacillus casei/paracasei a Lactobacillus plantarum. U starterových bakterií Lactococcus lactis subsp. lactis a Lactococcus lactis subsp. cremoris nebyla dekarboxylázová aktivita detekována., The aim of the work was to describe the development of selected biogenic amines (histamine, tyramine, putrescine and cadaverine) in 4 layers of Dutch-type cheese (Edam cheese) depending on 3 ripening/storage regimes during a 98-day period. Biogenic amines were analysed by means of ion-exchange chromatography. A further goal was to identify microbial sources of biogenic amines in the material analysed. Phenotype characterization and repetitive sequence-based PCR fingerprinting were used to identify the isolated bacteria. The highest content of tyramine, putrescine and cadaverine was determined in cheeses stored in a ripening cellar at a temperature of 10°C during the whole observation period. Lower biogenic amines content was determined in samples which were moved into a cold storage device (5°C) after 38 days of storage in a ripening cellar (10°C). The lowest concentrations of biogenic amines were detected in cheeses which were moved into a cold storage device (5°C) after 23 days of storage in a ripening cellar (10°C). During the 98-day period, histamine was not detected in any of the regimes. Within the cheeses analysed, non-starter lactic acid bacteria Lactobacillus curvatus, Lactobacillus casei/paracasei and Lactobacillus plantarum were detected as the main producers of the biogenic amines tested. In starter bacteria Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. cremoris the decarboxylase activity tested was not detected.

A total of 151 bacterial isolates were recovered from different developmental stages (larvae, nymphs and adults) of field-collected ticks (67 strains from Ixodes ricinus, 38 from Dermacentor reticulatus, 46 from Haemaphysalis concinna). Microorganisms were identified by means of 16S rRNA gene sequencing. Almost 87 % of the strains belonged to G(+) bacteria with predominantly occurring genera Bacillus and Paenibacillus. Other G(+) strains included Arthrobacter, Corynebacterium, Frigoribacterium, Kocuria, Microbacterium, Micrococcus, Plantibacter, Rhodococcus, Rothia, and Staphylococcus. G(-) strains occurred less frequently, comprising genera Advenella, Pseudomonas, Rahnella, Stenotrophomonas, and Xanthomonas. Several strains of medical importance were found, namely Advenella incenata, Corynebacterium aurimucosum, Microbacterium oxydans, M. schleiferi, Staphylococcus spp., and Stenotrophomonas maltophilia. Data on cultivable microbial diversity in Eurasian tick species D. reticulatus and H. concinna are given, along with the extension of present knowledge concerning bacterial flora of I. ricinus.

Katedra teorie a technologie výbušnin, Dokončená práce s úspěšnou obhajobou