Inoculation of soybean with Bradyrhizobium japonicum is often unsuccessful owing to the failure of inoculum strains to nodulate soybeans (Glycine max (L.) Merr.) in the presence of indigenous strains of rhizobia in soil. Previous studies have shown that it is possible to reduce nodulation with indigenous strains of rhizobia by amending the soil with a bacteriophage specific for the indigenous strain. The objective of the current study was to determine whether the coating of seed with phage affected nodule occupancy and soybean growth. A phage specific for B. japonicum USDA 469 and a symbiotically superior strain of rhizobium (B. japonicum USDA 110) were coated together onto soybean seed and planted into both greenhouse and field soil previously inoculated with B. japonicum USDA 469. The phage coated onto seed reduced nodulation by B. japonicum USDA 469 to 48% occupancy, compared with 64% for the untreated control value. Nodulation by the superior inoculum strain was increased from 48 to 82% occupancy by coating seed with the homologous phage and B. japonicum USDA 110. The rate of nitrogenase activity (on a per plant basis) was increased by coating seed with the phage and B. japonicum USDA 110. No other plant or symbiotic parameters were affected by phage coating of seed. These results indicate that the nodulation of soybeans can be significantly affected by the coating of seed with phage specific for undesirable strains of rhizobia in soil and the concurrent coating of seed with desirable strains of rhizobia. Key words: competition, rhizobiophage, rhizobia, soybeans.

Addition of heavy metals to soils from sources such as biosolid application, smelter emissions, fertilizers, and the like may produce soil solution concentrations of Zn and Cd that can potentially restrict nodulation of legume crops such as white clover. To assess the effects of Zn and Cd on the early stages of nodulation of white clover, a solution culture study was conducted. Rhizobia [Rhizobium leguminosarum bv. trifolii] of a metal‐sensitive strain (USDA 2063) and a metal‐tolerant strain (USDA 2046) were inoculated into nutrient solution with white clover seedlings containing EGTA to buffer Zn2+ and Cd2+ activities. The calculated activities of Zn2+ were p = 8.00, 5.70, 5.25, and 5.00; the calculated activities of Cd2+ were p = 10.50, 9.50, 8.75, and 8.50. Phase‐contrast microscopy was used after staining roots with methylene blue to observe root hair infection at intervals of 1, 12, 24, 72, and 168 h. Few differences were observed between the sensitive and tolerant rhizobial strains. At the lowest Zn concentration, initial attachment of bacteria to root hairs was observed within 1 h. At the highest Zn concentration, attachment was not observed until 12 h. Also, at the highest Zn concentration, a delay was observed for up to 60 h and 4 d, respectively, for the first signs of root hair curling and infection thread formation. Shoot weight decreased with increasing Zn concentration. Few Cd‐induced effects on early stages of nodule development were observed. Cadmium was more toxic to plant growth than Zn. These results show that in addition to direct effects on the macro and microsymbiont, the process of nodulation is susceptible to the toxic effects of heavy metals.

Thirty-three strains of Bradyrhizobium japonicum within serogroup 110 were examined for genotypic diversity by using DNA-DNA hybridization analyses. The analysis of the DNA from 15 hydrogen-uptakenegative strains with the bradyrhizobial uptake hydrogenase probe pHU52 showed variation in degree of homology and restriction fragment length polymorphism of EcoRI-restricted DNA. Clustering analysis of the 33 strains on the basis of DNA-DNA hybridization analysis with four restriction enzymes and with the bradyrhizobial nodulation locus, pRJUT10, as probe indicated the existence of four groups of strains, which were less than 70%o similar. Restriction digestion of genomic DNA with BamHI and DNA-DNA hybridization with pRJUT10 permitted classification of each of the strains according to a specific fingerprint pattern.

Thirty-four strains of Bradyrhizobium japonicum within serogroup 110 were examined for phenotypic diversity. The strains differed in their abilities to nodulate and fix dinitrogen with Glycine max (L.) Merr. cv. Williams. Thirteen strains expressed uptake hydrogenase activity when induced as free-living cultures in the presence of 2% hydrogen and oxygen. Six bacteriophage susceptibility reactions were observed. Each of the strains produced either a large, mucoid or a small, dry colony morphology, but colony type was not related to effectiveness for nitrogen fixation.

A total of 20 isolates of lactic acid bacteria (LAB) were isolated anaerobically from different food sources (Domiati cheese; raw milk and mixed pickles). Three out of 20 isolates showed high inhibition of growth pathogenic bacteria by well diffusion assay method and therefore they were chosen for bacteriocin production and further studies. The selected isolates were identified based on morphological, biochemical and MALDI-TOF mass spectrometry. All of the tested species gave a score value between 2.116 to 2.165 (100%) were correctly identified by MALDI-TOF-MS to the genus and species levels. They were identified as L. brevis, L. plantarum and L. fermentum. The bacteriocin was purified by salt precipitation and gel chromatography methods. The molecular weight was determined by SDS-PAGE and amino acid composition was also analysed. The purified bacteriocin was characterized and found to be thermostable at temperatures up to 90°C for 30min, pH from 3 to 11 and its activity improved in the presence of Tween 80, SDS and EDTA. The contents of bacteriocin from the acidic amino acid residues aspartic + glutamic (asp+glu) were 0.74% for all tested samples. The contents of the basic amino acids argnine + lysine + hisitidine (arg + lys + his) were 0.23% for all the tested samples.

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Trials for processing thc Egyptian lime juice for preservation were not successful. Bitterness, terpeney off-flavour, separation to a clear layer and a precipitate, the rapid deterioration and the loss of the original fresh taste and flavour are some problems that face the processing plant. In the present work, lime fruits urere tried instead of the extraction of lime juice. They were preserved with sugar, salt solutions or a mixture of them both in glass jars a t room temperature with a view of keeping the fruit cells intact. Chemical analysis, measuring the enzymatic activities, bacteriological analysis and organoleptic test of the preserved lime and the control proved statistically the validity of this new treatment. After 111 days, limes preserved in 15% sugar solution showed decrease of acidity, ascorbic acid, peroxidase/oxidase and pectinesterase. Bacteriological analysis showed an initial increase of bacterial count followed by a steady decrease till the end of the storage period. No mould (fungi) growth, nor E. coli were found. The predominant microorganisms were lactic acid bacteria, particularly Lactobacillus plantaw r n . Organoleptic tcst proved the absence of bitterness, terpeney off-flavour, separation and precipitation. A good taste and flavour were found. The natural inhibition and inactivation of enzymes was suggested for the stability of the lime fruits stored in solutions a t room temperature.

A total of 87 isolates of lactic acid bacteria (LAB) were isolated anaerobically from different food sources (yoghurt; Domiati cheese; fresh and fermented milk; mixed pickles and green olives), as well as human breast milk and infant stools. Only ten isolates showed high tolerance to pH 3.0 for three hours and therefore they were chosen for other studies. The selected isolates were identified based on physiological, biochemical and MALDI-TOF mass spectrometry identification. The most frequently observed genus was Lactobacillus (8 isolates) and one isolate seemed to be Enterococcus faecium and another isolate showed that it is Bifidobacterium bifidium. All of the tested species with a score value between 2.000 to 2.484 (100%) were correctly identified by MALDI-TOF-MS to the genus and species levels. The majority of LAB species were tolerant to 0.3% bile salts for up to 4 hrs but L. fermentum was the most tolerant. Four species exhibited partial bile salt hydrolase activity. All of the species survived in 1 mg/ml pancreatin for 4 hrs. However, two of them showed 1/10 decrease in their numbers. Eight species were non haemolytic. Most of the tested species were resistant to penicillin (10 µg), ciprofloxacin (5 µg), gentamycin (10 µg) and streptomycin (10µg). However other species showed variable resistance against the ten tested antibiotics according to NCCLS. The cell free supernatant of L. acidophilus (IS9) showed the highest antimicrobial property against all the indicator pathogens tested specially Staphylococcus aureus and Klebsiella pneumoniae. Therefore, these 10 species were found, in vitro, to possess desirable properties in order to use as probiotic for human consumption.