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Y M Barnet

Publications and source records attributed to Y M Barnet.

10 recordsLinked to original sources
PubMed1987

Environmental Factors Influencing Numbers of Rhizobium leguminosarum biovar trifolii and Its Bacteriophages in Two Field Soils.

Fluctuations in numbers of Rhizobium leguminosarum biovar trifolii and its bacteriophages in two fields with different soil types were followed during a 17-month period in 1981 and 1982. Mean levels of both phage and rhizobia varied significantly (P < 0.05) on different occasions, with rhizobial levels varying from 1.6 x 10 to 2.0 x 10 cell per g of soil and phage from 0 to 1.7 x 10 PFU/g of soil. Multivariate regression analysis showed rhizobial levels to be significantly and positively related to vegetation height and solar radiation, but not to mean temperature, precipitation, soil matric potential, or soil type. Rhizobiophage concentrations were significantly and positively related to soil matric potential and vegetation height. They were reduced in the silty clay loam soil, although the presence of 34% clay did not prevent phage multiplication and the occurrence of high phage levels.

Journal Article↗
PubMed1984

The effect of suspended particulate material on cyanobacteria--cyanophage interactions in liquid culture.

The effect of the lytic phage LPP-DUN1 on the cyanobacterium Plectonema boryanum has been investigated in batch and in continuous cultures in the presence and absence of silt. In batch culture Plectonema without added phage grew normally; the presence of phage caused rapid lysis of the cyanobacterium and the addition of silt prevented lysis by the phage. In continuous culture the numbers of cyanobacterial cells and phage particles oscillated in a reciprocal manner, but the addition of silt damped down the oscillations in Plectonema biomass without decreasing the numbers of phage particles isolated from the cultures. The presence of silt thus appears to protect the cyanobacterium from lysis by phage, although the total numbers of phage particles are relatively unaffected by the silt, at least in the short-term.

Bacteriophages↗
PubMed1980

The effect of rhizobiophages on populations of Rhizobium trifolii in the root zone of clover plants.

The effect of rhizobiophages CT3 and CT4 on Rhizobium trifolii SU91 and SU36, respectively, was examined. These phage-susceptible strains were used, either singly or paired with a competing phage-resistant type as inoculum for Trifolium subterraneum plants growing in vitro in agar medium. Addition of bacteriophage to single strain experiments produced no significant effects on total bacterial numbers, nodulation, or plant dry weight. However, when phages were added to the paired inocula, significant decreases in counts of the susceptible strain were observed, frequently accompanied by a rise in numbers of the resistnt type. An increase in the proportion of ineffective variants of the susceptible rhizobia was also observed, although plant dry weights and nodule numbers were not altered. These effects were dependent only upon a difference in phage susceptibility of the bacteria and were obtained even when the competing strain was only partially resistant and a relativly poor competitor.

Bacteriophages↗
PubMed1979

Effect of a bacteriophage on the colonisation and nodulation of clover roots by a strain of Rhizobium trifolii.

The presence of a virulent bacteriophage in the root zone of clover growing in seedling agar under controlled environments (14--17 and 19--23 degrees C) produced changes in the persistence and symbiotic effectiveness of a susceptible strain of Rhizobium trifolii. The phage reduced the rhizoplane population of rhizobia and led to the appearance of variant substrains which were less susceptible to the bacteriophage and mostly ineffective in symbiotic nitrogen fixation. Some were also changed in colonial morphology and nutritional requirements. At the higher temperature, the frequency of bacterial variants increased and the number of nodules due to the parent strain decreased. A large initial population of bacteriophage was able to reduce, but generally did not completely suppress, nodulation.

Bacteriophages↗
PubMed1979

Effect of a bacteriophage on colonisation and nodulation of clover roots by paired strains of Rhizobium trifolii.

The effect of a virulent bacteriophage on the competitive behaviour of paired strains of Rhizobium trifolii in the root zone of clover plants was examined. The presence of bacteriophage reduced the population density of susceptible strains on the root surface and, in nodulation, favoured resistant or even partially resistant strains which were otherwise less able to form nodules. These effects occurred with different growth temperatures, host species, and ratios of strains in the inoculum.

Antibiosis↗
PubMed1979

Properties of Rhizobium trifolii isolates surviving exposure to specific bacteriophage.

Six strains of Rhizobium trifolii were exposed to specific bacteriophages and the properties of 10 surviving clones of each studied. Two temperate bacteriophages produced clones which were lysogenic but showed no changes in colony form, symbiotic properties, or somatic antigens. Of forty clones selected by exposure to four other bacteriophages, none were lysogenic although there was some indication of unusually long association of phage with bacteria in infected cultures. Seventeen of these clones were changed in symbiotic properties, 15 in colony morphology, and 13 in somatic cross-reaction with the parent. Unexpectedly, despite stringent selection conditions, 28 were still either partially or completely susceptible to the selecting phage.

Bacteriophages↗
PubMed1975

Exopolysaccharide depolymerases induced by Rhizobium bacteriophages.

Enzymes induced by two Rhizobium trifolii bacteriophages caused depolymerization of exopolysaccharides from most R. trifolii and R. leguminosarum strains tested, but did not, in general, attack the exopolysaccharides of R. meliloti, the slow-growing rhizobia, or Agrobacterium. Ca2+ and (or) Mg2+ were required for enzyme activity. In all strains tested, depolymerization of exopolysaccharide occurred when there was successful phage infection, but depolymerization also occurred with exopolysaccharides from nonsusceptible strains.

Bacteriophages↗