The influence of a host's diet on Butyrivibrio and Pseudobutyrivibrio populations was investigated by competitive PCR. Specific primers were designed and competitive PCRs developed for both groups. Results (from 4 cows with different diets) suggested that high-fiber intake essentially increases the Butyrivibrio amounts in the rumen, whereas high-energy food additives lead to its suppression. The Pseudobutyrivibrio concentration also changed during the experiment but without any significant relation to the host's diet.

Different microfungi were isolated from salty soil and hypersaline water samples, taken from the extreme environment of operating marine solar salterns. The filamentous fungus most frequently and repeatedly isolated was identified as the pathogen Aspergillus fumigatus. Because of its great morphological variability and mycotoxin production ability, 50 A. fumigatus isolates were selected for additional characterisation by their secondary metabolites profile, which was determined by thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). At standard conditions 45% of the isolated strains produced different mycotoxins and in ecological conditions prevailing in the saltern (high salinity and temperature) production of important mycotoxins (verruculogen, fumitremorgins B and C, fumigaclavine A) was lowered or inhibited.

No abstract

Recently developed molecular biology approaches make possible the detailed genetic, taxonomic and ecological examination of microorganisms from various habitats. Animal gut represents one of the most complex microbial ecosystems with a large degree of microbial biodiversity present. Bacteria inhabiting the gut usually play important roles in metabolic transformations of substrates and sometimes, e.g. in ruminants, they make the basis for an obligate symbiosis with the host. Here we discuss molecular microbiology as a strategy for examination of gut bacteria, concentrating on a typical and in such environment dominant group of strictly anaerobic Gram-negative bacteria from the phylogenetic group Cytophaga/Flexibacter/Bacteroides. The bacteria from the genus Prevotella are the most abundant Gram-negative bacteria in the rumen and form a distinctive phylogenetic cluster, clearly separated from prevotellas isolated from other ecological niches. They may represent a good choice for a model organism in genetic manipulation experiments and for studies of gene transfer mechanisms taking place in the gut. The molecular tools for detection and monitoring of ruminal prevotellas are discussed.

The development and preliminary use of two different molecular approaches for rapid enumeration and monitoring of ruminal prevotellas are described. Several oligonucleotide DNA probes, specific for the genus Prevotella and the species P. ruminicola and P. bryantii were labeled with various fluorochromes and used in in situ hybridization experiments. Epifluorescent microscopy was successfully used for the detection of fluorescent signal emitted by the probes in pure and mixed culture samples. The enumeration of the target cells and the analysis of the crude rumen fluid proved to be difficult, however, mainly due to the autofluorescent background and nonhomogeneous distribution of the cells on the microscope slide. The development of a competitive PCR system for ruminal prevotellas is described and the preliminary results of the rumen fluid analysis from a black-and-white Holstein cow are given.