Increased Likelihood of High Nitrous Oxide (N2O) Exchange in Soils at Reduced Microbial Diversity

Rare soil organisms are normally considered of less importance for ecosystem functioning. We present results that oppose this view. In otherwise well-aerated soils, anaerobic/microaerophilic production or consumption of the trace gas N2O occurs in small soil volumes, when intense decomposition activity at the site leads to local oxygen depletion. At such patch scales, the control of microbial growth and oxygen consumption may depend on the specific organisms present. We assessed N2O turnover in an experiment, where soil dilution from 10−2 over 10−4 to 10−6 followed by microbial regrowth resulted in similar microbial biomass and respiration but reduced diversity. We found an increasing number of very high N2O turnover rates when soil dilution increased from 10−2 over 10−4 to 10−6, as revealed from a significantly increased skewness of the frequency distribution of N2O turnover levels. N2O turnover also tended to increase (p = 0.08) by 20–30% when soil was diluted from 10−2 to 10−6. This suggests that rare soil organisms regulate the local activity of fast-growing microorganisms and thus reduce the probability that anoxic/microaerophilic soil volumes develop. Future studies may reveal which less abundant organisms prevent development of anoxic/microaerophilic conditions in well-aerated soils.

Occurrence and Diversity of Soil Microflora in Potato Fields of Bangladesh

Microflora from potato rhizosphere soil was isolated from different potato fields of Bangladesh. Seventeen soil samples were analyzed for the presence of microflora in selected potato field soils. Seven fungal species and one bacterium species were morphologically characterized using soil dilution and streak plate methods. The predominant fungi isolated including Alternaria sp., Aspergillus sp., Penicillium sp., Rhizopus sp., Bipolaris sp., Phytophthora sp., Fusarium sp. and one bacterium was identified as Ralstonia solanacearum. Individual colonies of fungi and bacteria were counted on Potato Dextrose Agar (PDA), V8 juice Agar and their presence in soil was compared in respect of different locations of potato fields. The occurrence of Phytophthora sp. was medium in Tongibari and lower in Singair Union, Sonargaon, Matlab Dakshin, Gobindaganj, Palashbari, Gopinathpur and Bagmara. The highest counts of R. solanacearum were found in Singair Union, Tongibari and Daudkandi and the lowest counts were made in Palashbari and Bagmara. This was the first reported examination of the microbial diversity of soil microflora in some selected potato fields of Bangladesh.

Patterns of Occurrence and Activity of Entomopathogenic Fungi in the Algarve (Portugal) Using Different Isolation Methods

Entomopathogenic fungi (EPF) are distributed in natural and agricultural soils worldwide. To investigate EPF occurrence in different botanical habitats and soil-ecoregions, we surveyed 50 georeferenced localities in the spring of 2016 across the Algarve region (South Portugal). Additionally, we compared three EPF isolation methods: insect baiting in untreated or pre-dried-soil and soil dilution plating on a selective medium. We hypothesized that forest habitats (oak and pine semi-natural areas) and the acidic soil ecoregion may favor EPF occurrence. Overall, EPF species were present in 68% of sites, widely distributed throughout the Algarve. The use of selective media resulted in higher recovery of EPF than did either soil-baiting method. Contrary to our hypothesis, neither vegetation type nor ecoregion appeared to influence EPF occurrence. Traditional and molecular methods confirmed the presence of five EPF species. Beauveria bassiana (34% of sites), was the most frequently detected EPF, using pre-dried soil baiting and soil dilution methods. However, baiting untreated soil recovered Fusarium solani more frequently (26% of sites), demonstrating the utility of using multiple isolation methods. We also found Fusarium oxysporum, Purpureocillium lilacinum and Metarhizium anisopliae in 14%, 8% and 2% of the sites, respectively. Three abiotic variables (pH, soil organic matter and Mg) explained 96% of the variability of the entomopathogen community (EPF and entomopathogenic nematodes) in a canonical correspondence analysis, confirming the congruence of the soil properties that drive the assemblage of both entomopathogens. This study expands the knowledge of EPF distribution in natural and cultivated Mediterranean habitats.

Cultured Microfungal Communities in Biological Soil Crusts and Bare Soils at the Tabernas Desert, Spain

We examined the variations in microfungal communities from different surface types (cyanobacterial crusts, lichen-dominated crusts, and noncrusted bare surface) at two different positions—north-oriented slope and sun-exposed plain in the Tabernas Desert, Spain. A total of 77 species from 46 genera was isolated using the soil dilution plate method. The studied mycobiota, similar to the majority of desert mycobiotas, was dominated by melanin-containing species. However, in the Tabernas crusts, unlike the studied crusts of the Negev Desert (Israel) and the Tengger Desert (China), melanized fungi with large multicellular spores were much less abundantly represented, while the thermotolerant group, Aspergillus spp., remarkably contributed to the communities’ structure. Density of microfungal isolates positively correlated with chlorophyll content indicating possible significant influence of organic matter content on fungal biomass. The variations in crust composition, biomass, and the position of habitats were accompanied by the variations in microfungal community structure, diversity level, and isolate densities, with the communities at the plain sun-exposed position being much less variable than the communities at the north-oriented position. The study shows that microclimatic and edaphic factors play an essential role in the development of crust and noncrust microfungal communities, and their structure can be a sensitive indicator of changing environmental conditions at a microscale.

Isolation of potential fluorescent pseudomonads from Kuini (Mangifera odorata) planted soil and their potential as biofertilizer

Pseudomonas sp. are known to be good Plant Growth Promoting Rhizobacteria (PGPR). In this study, Pseudomonas sp. were isolated from soil planted with kuini (Mangifera odorata) using soil dilution method and spread onto King’s B media. Five isolates of Pseudomonas sp. were observed to give promising results in the phytohormone and antimicrobial test conducted. These isolates are Pseudomonas sp. isolate K24pf, K29pf, K32pf, K33pf and K37pf. From the 5 potential isolates, Pseudomonas sp. isolate K29pf was chosen because it showed potential activity in producing marked amounts of Indole-3-Acetic Acid and gibberellic acid. Pseudomonas sp. isolate K29pf also produced antimicrobial activities towards Ralstonia solanacearum, Erwinia caratovora, Erwinia mallotivora and Colletotrichum gloeosporioides. Seed germination test showed that Pseudomonas sp. isolate K29pf was able to promote approximately 90% growth of Brassica chinensis seeds. Pot trial conducted showed that Treatment 3 (+OF+PGPR) was able to increase Brassica chinensis root by 36.5% and 28.4% of its biomass compared to treatment using Treatment 1 (+OF).

A Study on Soil Thermophilic and Thermotolerant Fungi in Thamar-Yemen

Thirty-eight soil samples were collected from different sites in Thamar province during the period from 4/2012 to 2/2013.The direct plate, and dilution plates methods were followed to isolation of counting colony forming units, the potato carrot agar (PCA) and Emerson's media were used A total of 23 fungi belong to (14) genera were isolated, they include (11) Hyphomycetes, (10) Ascomycetes, and (2) Zygomycetes besides black and white sterile mycelium. A fourteen isolates were regarded asnewly record for Yemeni mycobiota,they include Acremonium murorum, Acrophialophorafusispora, Chaetomiumatrobrunneum, C.gracile,C.strumarium, C.therophilevar.coprophpile, Corynascussepedonium ,Emericellarugulosa, Melanocarpusalbomyces, paecelomycesinflatus Papulosporathermophila, Rhizomucormiehi, Scytalidiumthermophilum, and Talromycesthermophilus Soil dilution method showed that the colony forming units (CFUs)in soil had seasonal fluctuation , they were significantly higher (36667) during moderate/humid month than cold/dry months (20400) (p<0.05), while the total similarity% is high between fungal genera which were isolated during the two periods (78.57%) .A test of 15 isolates to produce cellulase, amylase, lipase, protease, xylanase and phenoloxidase showed a different activities in number of enzymes and levels of production. Corynascussepedonium, Eemericellanedulans and Malbrancheacinnamomea gave a positive result for all enzymes

Isolation of Potential Alkaliphilic Cellulase-Producer Strains from Limestone Area of Perlis

Alkaliphilic cellulases-producer fungi were isolated from soil of limestone areas in Perlis. The potential strain was isolated by soil dilution plate method on enriched selective medium using CMC as substrate at different pH levels. Eleven isolates of different morphological colonies were screened using the hydrolysis capacity test by Gram’s iodine. Out of eleven colonies, five showed positive results as the hydrolysis zone formed. BK1 showed the highest hydrolysis capacity among all sample strains for every pH levels. Eventually, four strains were selected to be further explored as cellulolytic fungi for the production of alkaline cellulase in the future.

Analysis on Cultivable Fungal Community Structures in Farmland Soil in Different Latitudes of Heilongjiang Province

Soil microorganism is a very important component part of soil ecosystem, this paper studied composition and diversity of the cultivable fungal communities in farmland soil in Tahe, Dailing, Maoershan three different latitude regions by means of soil dilution plate and soil particle plate and culture on standard media. The results indicated that the tendency of number of cultivable fungal in farmland soil in different regions: Tahe>Dailing>Maoershan. Scopulariopsis, Chaetomium, Neurospor, Cephalosporium, Aureobasidium and Penicillium occured in farmland soil of three samples, and they were common groups. The cultivable fungal diversities in farmland soil of three sampling regions were no significantly difference, and Dailing was the highest in four different diversity indexes.

Microfungi in the soil beneath common oak and their effect on Armillaria occurrence

Microfungal assemblages in a soil beneath 30- and 50·year-old oaks and their 2-year-old stumps were studied using the soil dilution plate method. A total of 98 culturable microfungi were isolated. Compared to the living oaks before felling and the control living oaks, the density of <i>Mortierella macrocystis, Penicillium jonczewskii, Pseudogymnoascus roseus Sporothrix schenckii, Tolypoccladiumum inflatum</i> and <i>Umbelopsis vinacea</i> sigificantly inacased in the soil beneath slumps in the 32- and 52-year-old stands. Density of <i>Aspergillus kanagawaensis, Monodictys lepraria, P. daleae</i> and sterile dematiaceous hyphomycetes increased significantly in the 32-year-old stand and <i>Chrysosporium merdarium</i> in the 52·year-old stand. These fungi are known 'stimulants' of <i>Armillaria</i> rhizomorph formation. It is suggested that the increase in density of <i>Armillaria</i> rhizomorph 'stimulants' in a soil beneath oak stumps may increase the possibility of colonization of stumps by <i>Armillaria</i>.

Fertility Evaluation of Limed Brazilian Soil Polluted with Scrap Metal Residue

The aim of this work was to characterize the main inorganic contaminants and evaluate the effect of lime addition, combined with soil dilution with uncontaminated soil, as a strategy for mitigation of these contaminants present in a soil polluted with auto scrap. The experiment was performed in a greenhouse at Campinas (São Paulo State, Brazil) in plastic pots (3 dm−3). Five soil mixtures, obtained by mixing an uncontaminated soil sample with contaminated soil (0, 25, 50, 75, and 100% contaminated soil), were evaluated for soil fertility, availability of inorganic contaminants, and corn development. In addition to the expected changes in soil chemistry due to the addition of lime, only the availability of Fe and Mn in the soil mixtures was affected, while the available contents of Cu, Zn, Cd, Cr, Ni, and Pb increased to some extent in the soil mixtures with higher proportion of contaminated soil. Liming of 10 t ha−1followed by soil dilution at any proportion studied was not successful for mitigation of the inorganic contaminants to a desired level of soil fertility, as demonstrated by the available amounts extracted by the DTPA method (Zn, Pb, Cu, Ni, Cr, Cd) and hot water (B) still present in the soil. This fact was also proved by the phytotoxicity observed and caused by high amounts of B and Zn accumulating in the plant tissue.