Manuel Serrat Díaz

Isolation and characterisation of aerobic endospore forming Bacilli from sugarcane rhizosphere for the selection of strains with agriculture potentialities

Eighteen aerobic endospore forming strains were isolated from sugarcane rhizosphere in N-free medium. A phenotypic description and analysis of the 5′ end hypervariable region sequences of 16S rRNA revealed a high diversity of Bacillus and related genera. Isolates were identified, and four genera were obtained: seven strains belonged to Bacillus (Bacillaceae family), four belonged to Paenibacillus, six belonged to Brevibacillus and one strain was identified as Cohnella (Paenibacillaceae family). Four Brevibacillus strains showed in vitro inhibitory activity against plant pathogens fungi Curvularia and Fusarium. Seventy-four percent of the isolated bacteria grew on pectin as the only carbon source, showing polygalacturonase activity. Pectate lyase activity was detected for the first time in a Brevibacillus genus strain. All isolates showed endoglucanase activity. Calcium phosphate solubilisation was positive in 83.3% of the isolates, with higher values than those reported for Bacillus inorganic phosphate solubilising strains. High ethylene plant hormone secretion in the culture medium was detected in 22% of the bacteria. This is the first report of ethylene secretion in Paenibacillaceae isolates. Indole-3-acetic acid production was found in a Brevibacillus genus isolate. It was reported for the first time the presence of Cohnella genus strain on sugarcane rhizosphere bearing plant growth promoting traits. The sugarcane isolate Brevibacillus B65 was identified as a plant growth inoculant because it showed wider spectra of plant stimulation capabilities, including an antifungal effect, extracellular hydrolases secretion, inorganic phosphate solubilisation and plant hormone liberation. In this work, sugarcane was shown to be a suitable niche for finding aerobic endospore forming ‘Bacilli’ with agriculture biotechnological purposes.

The New Rhizospheric Bacteria Brevibacillus Benefits Eggplant and Peeper Growth and Productivity Under Organoponic System

Eggplant and pepper are horticulture crops with a worldwide distribution, dietary, and culinary importance. In developing countries, they are mainly cultivated under organic amendments as the organoponic system applied in Cuba. In the present research, the plant growth promoting strain B65 of Brevibacillus sp. was applied as inoculant on eggplant and pepper crops cultivated in two organoponics that belong to the urban agriculture program of Santiago de Cuba. Influence of B65 inoculum on plants’ growth and crops’ yield was evaluated. Inoculation of the strain B65 significantly increased plants’ height, number of flowers, and number of fruits per plant as fruits size, weight, and yield. It also increased the root fresh matter. The beneficial effects of B65 under organic amendments could be related with its previously reported plant growth-promoting traits. The present research shows for the first time biostimulating and biofertilizing effects of Brevibacillus sp. inoculation in horticulture crops and reveals that Brevibacillus sp. strain B65 could be applied as part of sustainable agriculture strategies.Eggplant and pepper are horticulture crops with a worldwide distribution, dietary, and culinary importance. In developing countries, they are mainly cultivated under organic amendments as the organoponic system applied in Cuba. In the present research, the plant growth promoting strain B65 of Brevibacillus sp. was applied as inoculant on eggplant and pepper crops cultivated in two organoponics that belong to the urban agriculture program of Santiago de Cuba. Influence of B65 inoculum on plants’ growth and crops’ yield was evaluated. Inoculation of the strain B65 significantly increased plants’ height, number of flowers, and number of fruits per plant as fruits size, weight, and yield. It also increased the root fresh matter. The beneficial effects of B65 under organic amendments could be related with its previously reported plant growth-promoting traits. The present research shows for the first time biostimulating and biofertilizing effects of Brevibacillus sp. inoculation in horticulture crops and reveals that Brevibacillus sp. strain B65 could be applied as part of sustainable agriculture strategies.

In vitro growth inhibition of Curvularia gudauskasii by Bacillus subtilis

Five rhizosphere Bacillus subtilis isolates were tested for in vitro antagonism against a sugarcane seedling pathogen strain of Curvularia gudauskasii. The isolate B. subtilis SR/B-16 was selected because it permanently inhibits 71% of fungal growth. Microscopic analysis of the antagonistic bacteria effects on C. gudauskasii revealed swelling and bulbous hyphae, vacuolated cytoplasm and no spore formation. The analysis of culture filtrates of SR/B-16 collected from stationary phase showed that they are responsible for the antifungal effects and for the abnormal shapes observed. However, bacterial culture efficiency is higher. The organic concentrated fraction of the extracts caused the same morphological changes as those caused by antifungal lipopeptides secreted by Bacillus species. The strain SR/B-16 can be used for the formulation of bioactive compounds for the treatment of C. gudauskasii diseases on sugarcane seedlings.