For evaluating N(2) fixation of diazotrophic bacteria, nitrogen-poor liquid media supplemented with at least 0.5% sugar and 0.2% agar are widely used for acetylene reduction assays. In such a soft gel medium, however, many N(2)-fixing soil bacteria generally show only trace acetylene reduction activity. Here, we report that use of a N(2) fixation medium solidified with gellan gum instead of aga...

soil salinity induces a stressful environment for soil micro-organisms and reduces their number and activity. the objective of this research is investigating the effect of different levels of salinity on some of soil biological indicators and also assessing the effect of two types of halotolerant rhizospheric bacteria on the value of these indexes in soil. 35 strains were isolated from saline r...

We studied controls on nitrification in an undisturbed water-limited ecosystem by inhibiting autotrophic nitrifying bacteria in soils with varying levels of vegetative cover. The activity of nitrifying bacteria was disrupted using nitrapyrin, 2-chloro-6-(trichloromethyl)-pyridine, under field conditions in three microenvironments (underneath shrubs, next to grasses and in bare soil). Ammonia-ox...

Bacteria that are capable of degrading polycyclic aromatic hydrocarbons were enumerated by incorporating soil and water dilutions together with fine particles of phenanthrene, a polycyclic aromatic hydrocarbon, into an agarose overlayer and pouring the mixture over a mineral salts underlayer. The phenanthrene-degrading bacteria embedded in the overlayer were recognized by a halo of clearing in ...

Degradation of polycyclic aromatic hydrocarbons (PAHs) and survival of bacteria in soil was investigated by applying different inoculation protocols. The soil was inoculated with Sphingomonas paucimobilis BA 2 and strain BP 9, which are able to degrade anthracene and pyrene, respectively. CFU of soil bacteria and of the introduced bacteria were monitored in native and sterilized soil at differe...

One DDT-contaminated soil and two uncontaminated soils were used to enumerate DDT-resistant microbes (bacteria, actinomycetes and fungi) by using soil dilution agar plates in media either with 150 mg DDT ml−1 or without DDT at different temperatures (25, 37 and 55◦C). Microbial populations in this study were significantly (p<0.001) affected by DDT in the growth medium. However, the numbers of m...

Advances in the growth of hitherto unculturable soil bacteria have emphasized the requirement for rapid bacterial identification methods. Due to the slow-growing strategy of microcolony-forming soil bacteria, successful fluorescence in situ hybridization (FISH) requires an rRNA enrichment step for visualization. In this study, catalyzed reporter deposition (CARD)-FISH was employed as an alterna...

Experiments were conducted to evaluate the potential of phosphate solubilizing bacteria (PSB) Bacillus megaterium and potassium solubilizing bacteria (KSB) Bacillus mucilaginosus inoculated in nutrient limited soil planted with eggplant. Results showed that rock P and K materials either applied singly or in combination did not significantly enhance soil availability of P and K. PSB increased hi...

soil biodiversity is the origin of considerable goods for maintenance and extension of above ground biodiversity and environmental soundness. this study was carried out in shirvan, mashhad and gonabad, three regions of razavi and northern khorasan provinces, to determine soil characteristics and biodiversity in natural systems of arid and semi-arid regions. in each studied system, 10 locations ...