Isolation, identification, and biocontrol of antagonistic bacterium against Botrytis cinerea after tomato harvest

ABSTRACT Tomato is one of the most important vegetables in the world. Decay after harvest is a major issue in the development of tomato industry. Currently, the most effective method for controlling decay after harvest is storage of tomato at low temperature combined with usage of chemical bactericide; however, long-term usage of chemical bactericide not only causes pathogen resistance but also is harmful for human health and environment. Biocontrol method for the management of disease after tomato harvest has great practical significance. In this study, antagonistic bacterium B-6-1 strain was isolated from the surface of tomato and identified as Enterobacter cowanii based on morphological characteristics and physiological and biochemical features combined with sequence analysis of 16SrDNA and ropB gene and construction of dendrogram. Effects of different concentrations of antagonistic bacterium E. cowanii suspension on antifungal activity after tomato harvest were analyzed by mycelium growth rate method. Results revealed that antifungal activity was also enhanced with increasing concentrations of antagonistic bacterium; inhibitory rates of 1 × 105 colony-forming units (cfu)/mL antagonistic bacterial solution on Fusarium verticillioides, Alternaria tenuissima, and Botrytis cinerea were 46.31%, 67.48%, and 75.67%, respectively. By using in vivo inoculation method, it was further confirmed that antagonistic bacterium could effectively inhibit the occurrence of B. cinerae after tomato harvest, biocontrol effect of 1 × 109 cfu/mL zymotic fluid reached up to 95.24%, and antagonistic bacterium E. cowanii has biocontrol potential against B. cinerea after harvest of fruits and vegetables.

Plant Growth Promotion and Root Colonization by EPS Producing Enterobacter sp. RZS5 under Heavy Metal Contaminated Soil.

The heavy metal resistant bacterium isolated from field soil and identified as Enterobacter sp. RZS5 tolerates a high concentration (100-2000 mM) of various heavy metal ions such as Mn2+, Ni2+, Zn2+, Cu2+, CO2+ and Fe2+ when grown in such environment and produces exopolysaccharides (EPS). Here, we have demonstrated EPS production by Enterobacter sp. RZS5 during 60 h of growth in yeast extract mannitol broth (YEMB). The yield increased by two fold after the addition of 60 M of Ca2+; 50 M of Fe2+ and 60 M of Mg2+ ions in YEMB, and the optimization of physico-chemical parameters. EPS was extracted with 30% (v/v) of isopropanol as against the commonly used 50% (v/v) isopropanol method. EPS-rich broth promoted seed germination, shoot height, root length, number of leaves and chlorophyll content of wheat (Triticum aestivum) and peanut (Arachis hypogaea) seeds. The higher colony-forming unit of Enterobacter sp. in soil inoculated with EPS rich broth of Enterobacter sp. indicated the root colonizing potential and rhizosphere competence of the isolate. The FTIR spectra of the EPS extract confirmed the presence of the functional group characteristics of EPS known to exhibit a high binding affinity towards certain metal ions. This overall growth and vigour in plants along with the effective root colonization, reflected the potential of the isolate as an efficient bio-inoculant in bioremediation.

Effects of different osmolarities on bacterial biofilm formation

Biofilm formation depends on several factors. The influence of different osmolarities on bacterial biofilm formation was studied. Two strains (Enterobacter sp. and Stenotrophomonas sp.) exhibited the most remarkable alterations. Biofilm formation is an important trait and its use has been associated to the protection of organisms against environmental stresses.

Growth response of maize plantlets inoculated with Enterobacter spp., as a model for alternative agriculture / Respuesta de plántulas de maíz inoculadas con Enterobacter spp. como un modelo de agricultura alternativa

A maize rhizosphere isolate was phenotypically and genotypically characterized and identifed as Enterobacter spp. bacterium. Germinated seeds were inoculated, the plantlets were sown in vermiculite and in soil and grown under laboratory and feld conditions, respectively. The adherence, colonization and plant growth promotion capability of Enterobacter sp. UAPS03001 was evaluated in "Rojo-Criollo" maize under laboratory conditions. Twenty days after inoculation, the treated plantlets showed larger biomass than non-inoculated ones. In feld grown plants, the kernel biomass was also greater in inoculated than in non-inoculated plants. The inoculation of maize sprouts with plant growth- promoting bacteria before their sowing in the feld would be an alternative practice for achieving successful yield in temporal agriculture.

En este trabajo se aisló una bacteria de la rizósfera de maíz, que fue caracterizada mediante métodos fenotípicos y genotípicos e identifcada como Enterobacter sp. UAPS03001. La bacteria fue inoculada en semillas de maíz "Rojo-Criollo" germinadas en forma axénica. Las semillas germinadas e inoculadas se plantaron en vermiculita y posteriormente las plántulas fueron cultivadas en vermiculita o en suelo, para evaluar el efecto promotor del crecimiento vegetal de dicha bacteria, bajo condiciones de laboratorio y de campo. Bajo condiciones de laboratorio, también se evaluó la capacidad de esta cepa para adherirse a las plantas de maíz y colonizarlas. Veinte días después de la inoculación, las plántulas inoculadas mostraron una biomasa mayor con referencia a las no inoculadas. En campo, la biomasa de la mazorca fue también mayor en las plantas inoculadas respecto de las plantas no inoculadas. La inoculación de germinados de maíz con una bacteria promotora del crecimiento vegetal y su posterior transferencia a campo podría ser una práctica alternativa para llevar a cabo una producción exitosa en agricultura de temporal.