Counting and size classification of active soil bacteria by fluorescence in situ hybridization with an rRNA oligonucleotide probe

Article Abstract:

A method that is capable of counting ribosome-active bacteria in soil and can categorize soil bacteria by size was developed. This method uses a fluorescence in situ hybridization technique that is predicated on binding of a rhodamine-labelled oligonucleotide probe to 16S ribosomal RNA. Use of the proposed procedure and fluorescence microscopy led to the identification of active soil bacteria according to their size groups. This method will be useful for phylogenetic probes and for automatic soil bacteria counting.

Measurement, Bacteria, Nucleic acid probes, Fluorescence microscopy, Ribosomal RNA, Soils, Soil analysis, Agricultural bacteriology, Bacteriology, Agricultural

Secondary metabolite- and endochitinase-dependent antagonism toward plant-pathogenic microfungi of Pseudomonas fluorescens isolates from sugar beet rhizosphere

Article Abstract:

A large collection of fluorescent pseudomonads isolated from the sugar beet rhizosphere for in vitro antagonism toward Pythium ultimum and Rhizoctonia solani was studied to provide a selection protocol for natural Pseudomomas strains. Both pathogens were inhibited by 2,4-diacetylphloroglucinol and viscosinamide. The assignment of different patterns of fungal antagonism to the biovars of P. fluorescens was examined in relation to an improved selection protocol for candidate strains in biological control.

Fungi, Physiological regulation, Biological control systems, Pseudomonas fluorescens, Antibiosis, Sugar beets, Sugar beet

Microgradients of microbial oxygen consumption in a barley rhizosphere modelsystem

Article Abstract:

The utilization of a microsensor technique for mapping the radial distribution of oxygen concentrations around barley roots grown in gel-stabilized soil suspension is discussed. Fick's laws of diffusion and a curve fitting approach for measured oxygen microprofiles were used to determine oxygen consumption by microbial respiration in the rhizosphere and in the root tissues. Variation in the microbial respiration and oxygen uptake between different roots was demonstrated.

Methods, Microbiology, Oxygen consumption, Oxygen consumption (Metabolism), Microelectrodes