Diversity Of Rhizobacteria Research Articles

The Diversity of Shallot Rhizomicrobiome and Twisted Disease Suppression with The Applicationof Bacillus spp. and Trichoderma asperellum

Twisted disease (Fusarium spp.) is an endemic disease that reduces shallot production in the coastal land area of Samas, Bantul, Yogyakarta. The application of Bacillus spp. can suppress the twisted disease by secreting secondary metabolites and enhancing soil suppressiveness. This study aimed to determine the effectiveness of adding spraying Bacillus spp. on the disease incidence, production of shallots, and their effect on the diversity of rhizomicrobiome by culture microbe approaches. Bacillus spp. with a density 108 cfu mL-1, Trichoderma asperellum 106 cfu mL-1 was applied by spraying to the shallot. Fungicide chlorothalonil, propiconazole, and prochloraz were used to control the disease. The diversity of rhizobacteria and fungi was analyzed using the ribosomal intergenic spacer analysis (RISA) method. Based on the analysis result, the addition of spraying B. velezensis B-27, combination B. velezensis B-27 and B. cereus RC76, and T. asperellum was unable to enhance the suppression of twisted disease, but it was able to enhance the production of shallot bulbs reaching 7.10, 7.80, and 8.43 ton ha-1. Furthermore, the result revealed the diversity of the rhizomicrobiome, spraying Bacillus sp. showed 39% differences in bacterial diversity with control while T. asperellum caused 43% difference in the diversity. Spraying Bacillus spp. has not been able to suppress the incidence of twisted diseases compared to control. However, the similar disease incidence on a spraying Bacillus spp. and control showed a higher production until 70% compared to control. This result showed that the addition of spraying Bacillus spp. able to increase the tolerance of shallot plants toward twisted disease.

Miscanthus biochar promotes growth of spring barley and shifts bacterial community structures including phosphorus and sulfur mobilizing bacteria

Biochar has shown great potentials in plant growth promotion but its effect on soil bacteria that potentially support plant growth is less well understood. In this study, the effect of biochar soil amendment was investigated on the growth of spring barley, its rhizobacteria diversity and the abundance of sulfur (S) and phosphorus (P) mobilizing bacteria. Furthermore, the S oxidation status was determined in soil, feedstock and biochar. Soil amendment with biochar made from Miscanthus x giganteus resulted in significantly increased growth of barley and grain formation four to seven fold. Further significant increases were found for the soil pH and abundances of rhizosphere soil bacteria capable of growing with tri-calcium phosphate, phosphate-esters, phosphonates or aromatic sulfonates as sole source of S or P. A stepwise regression model attributed 74% of the variation in plant growth to the abundances of P and S mobilizing bacteria. 16S rRNA gene based fingerprint analysis revealed a significant shift in the bacterial community structure upon biochar amendment that correlated significantly with the above mentioned changes (pH, plant growth, bacterial abundances). Under biochar amendment, up to 100 times increases in genera Brevundimonas known for P cycling and Arthrobacter and Cupriavidus previously involved in sulfonate desulfurization were identified via quantitative PCR. S k-edge XANES confirmed that the key S source sulfonate was largely absent in the applied biochar, thus bacterial mobilization of sulfonate-S may have originated from the soil.

Plant powder teabags: a novel and practical approach to resolve culturability and diversity of rhizobacteria.

We have developed teabags packed with dehydrated plant powders, without any supplements, for preparation of plant infusions necessary to develop media for culturing rhizobacteria. These bacteria are efficiently cultivated on such plant teabag culture media, with better progressive in situ recoverability compared to standard chemically synthetic culture media. Combining various plant-based culture media and incubation conditions enabled us to resolve unique denaturing gradient gel electrophoresis (DGGE) bands that were not resolved by tested standard culture media. Based on polymerase chain reaction PCR-DGGE of 16S rDNA fingerprints and sequencing, the plant teabag culture media supported higher diversity and significant increases in the richness of endo-rhizobacteria, namely Gammaproteobacteria (Enterobacteriaceae) and predominantly Alphaproteobacteria (Rhizobiaceae). This culminated in greater retrieval of the rhizobacteria taxa associated with the plant roots. We conclude that the plant teabag culture medium by itself, without any nutritional supplements, is sufficient and efficient for recovering and mirroring the complex and diverse communities of rhizobacteria. Our message to fellow microbial ecologists is: simply dehydrate your plant canopy, teabag it and soak it to prepare your culture media, with no need for any additional supplementary nutrients.

Characterization of Plant-Growth-Promoting Effects and Concurrent Promotion of Heavy Metal Accumulation in the Tissues of the Plants Grown in The Polluted Soil by Burkholderia Strain LD-11

Plant-growth-promoting (PGP) bacteria especially with the resistance to multiple heavy metals are helpful to phytoremediation. Further development of PGP bacteria is very necessary because of the extreme diversity of plants, soils, and heavy metal pollution. A Burkholderia sp. strain, numbered LD-11, was isolated, which showed resistances to multiple heavy metals and antibiotics. It can produce indole-3-acetic acid, 1-aminocyclopropane-1-carboxylic acid deaminase and siderophores. Inoculation with the LD-11 improved germination of seeds of the investigated vegetable plants in the presence of Cu, promoted elongation of roots and hypocotyledonary axes, enhanced the dry weights of the plants grown in the soils polluted with Cu and/or Pb, and increased activity of the soil urease and the rhizobacteria diversity. Inoculation with the LD-11 significantly enhanced Cu and/or Pb accumulation especially in the roots of the plants grown in the polluted soils. Notably, LD-11 could produce siderophores in the presence of Cu. Conclusively, the PGP effects and concurrent heavy metal accumulation in the plant tissues results from combined effects of the above-mentioned multiple factors. Cu is an important element that represses production of the siderophore by the bacteria. Phytoremediation by synergistic use of the investigated plants and the bacterial strain LD-11 is a phytoextraction process.

Influence of Soil and Plant Types on Diversity of Rhizobacteria

Biodiversity is an important ingredient of environmental conservation and is central to agriculture production. Most microbial diversity of the soil ecosystem is confined to the rhizosphere. Rhizodeposition through plant root exudates plays a major role in defining resident microflora, which differs from that in bulk soil. Rhizobacterial diversity is influenced by both plant and soil type. Soil factors, plant root exudates and agricultural management are the factors that determine the community composition within the rhizosphere.

Effects of genetically modified potatoes with increased zeaxanthin content on the abundance and diversity of rhizobacteria with in vitro antagonistic activity do not exceed natural variability among cultivars

To assess potential effects of genetically modified (GM) potatoes on the abundance and diversity of rhizobacteria with in vitro antagonistic activity in relation to natural variability among cultivars, two GM potato lines accumulating the carotenoid zeaxanthin in their tubers, the parental cultivar and four additional commercial cultivars were planted at two field sites in Germany. Rhizosphere samples were taken at three developmental stages of the plants. A total of 3,985 bacteria isolated from the rhizosphere were screened for their in vitro antagonistic activity towards Rhizoctonia solani, Verticillium dahliae and Phytophthora infestans using a dual-culture assay. Genotypic characterisation, 16S rRNA gene sequencing and antifungal metabolite analysis was performed to characterize the 595 antagonists obtained. The 16S rRNA gene-based identification of in vitro antagonists revealed strong site-dependent differences in their taxonomic composition. This study showed that the site was the overriding factor determining the proportion and diversity of antagonists from the rhizosphere of potato while the effect of the genetic modification on the proportion of antagonists obtained did not exceed natural variability among the five commercial cultivars tested.

A broad range of themes in Microbial Biotechnology

In the November issue of Microbial Biotechnology a series of relevant articles were published regarding energy generation, thermostable enzymes, influence of transgenic plants on microbes that live in the rhizosphere of plants, degradation of hormones, identification of pathogens, and the use of phage to control bacterial populations. This abundant selection of articles reflects that Microbial Biotechnology is attracting interest from a wide range of fields with the aim of placing science within the prospect of future industrial developments. One of the themes that has attracted a good number of articles in 2008 has been energy generation. The November issue brought three relevant articles. One of them dealt with microbial fuel cells (MFCs), which are based on the use of microorganisms as biocatalysts to convert chemical energy contained in electron donors to electrical energy. Microbial fuel cells are considered to have potential application in the domains of power supply, biological oxygen demand sensors and especially in sustainable wastewater treatment. However, a number of limitations appear in the system and one of the approaches to overcome a number of these limitations was described by Pham and colleagues (2008) in the previous issue of Microbial Biotechnology. These authors show that the application of high shear rates enriched an anodophilic microbial consortium in MFC that resulted in higher performance. Enrichment at a shear rate of about 120 s

Diversity of Root Bacteria from Peanut Cropping Systems

Abstract Rhizobacteria play an important role in sustainable agriculture via plant growth and biological control of pests in a number of ecosystems. Understanding the interactions of crop rotation and rhizobacteria on peanut production is a critical research need. Development of a database on the rhizobacteria obtained from continuous and rotational fields of peanut was initiated in 1997 and terminated in 2000. Peanut was planted in monoculture for 4 yr. In rotational plots, peanut, cotton, corn, and peanut were planted in sequence. Rhizobacteria were isolated from the roots of crop plants grown in a Norfolk soil near Florence, SC. These isolates were identified by composition of fatty acids from gas chromatography analysis (GC/FAME). Arthrobacter and Bacillus were the major genera from non-rhizosphere soils. At initiation of this study in July 1997, the plots selected for continuous peanut had more diversity in rhizobacteria than those plots selected for rotation. In July 2000, rhizobacteria diversity was greater from peanut roots in the rotation cropping system than continuous peanut. Even though rhizobacteria diversity was greater in the rotation system, higher peanut yields were recorded in the continuous peanut system in 2000. Burkholderia spp. were always isolated from the peanut and other crop rhizospheres at each sampling date.

Influence of enhanced malate dehydrogenase expression by alfalfa on diversity of rhizobacteria and soil nutrient availability

Transgenic alfalfa over-expressing a nodule-enhanced malate dehydrogenase (neMDH) cDNA and untransformed alfalfa plants were grown at the same field site and rhizosphere soils collected after 53 weeks of plant growth. These alfalfa lines differ in the amount and composition of root organic acids produced and exuded into the rhizosphere. Nucleotide sequencing of PCR-based 16S ribosomal DNA (rDNA) clone libraries and Biolog™ GN microtiter plates were employed to assess the activity of naturally occurring rhizobacteria in the two alfalfa rhizospheres. Selected macro- and micro-elements in the two alfalfa rhizosphere soils were also measured. Analysis of 240 16S rDNA clone sequences indicated the existence of about 11 bacterial phyla and their major subdivisions in the two alfalfa rhizosphere samples. There were qualitative changes in the abundance of bacterial phylogenetic groups between rhizosphere soils of transgenic and untransformed alfalfa. Carbon substrate utilization profiles suggested that rhizosphere samples from transgenic alfalfa had significantly greater microbial functional diversity compared with rhizosphere samples from untransformed alfalfa. The concentrations of nitric acid extractable P, K, Mn, Zn and Cu increased significantly in the transgenic alfalfa rhizosphere compared with the untransformed alfalfa rhizosphere. These observations indicate that organic acids produced by plant roots significantly influence rhizosphere microbial diversity and availability of macro- and micro-nutrients and demonstrate the utility of such trangenic plants as tools for studying the potential impact of plant root exudates on soil microbial ecosystems.