Native Bacillus paralicheniformis isolate as a potential agent for phytopathogenic nematodes control.

Phytopathogenic nematodes (PPNs) are responsible for substantial damages within agricultural crops worldwide which can be controlled employing beneficial microorganisms and/or their metabolites in an ecofriendly way. Nevertheless, the success of the control regards not only on the virulence of the strains or the toxicity of their metabolites but also on their ability to colonize and remain in the rhizospheric environment, particularly in those crops affected by abiotic stresses promoted by the climate change. Consequently, the bioprospection of beneficial microorganisms able to control PPNs and to thrive in adverse conditions has attracted attention. On this way, deserts are perfect ecological niches to isolate microorganisms adapted to harsh enviroments. The purpose of this research was to isolate and characterize bacteria from rhizospheric soil samples collected in the Northwestern Desert of Mexico with potential for PPNs control. As first screening, secretomes of each isolate were tested in vitro for nematicidal activity (NA). Then, activities from secretomes and endospores from the selected isolate were confirmed in vivo assays. From 100 thermotolerant isolates, the secretome of the isolate identified as Bacillus paralicheniformis TB197 showed the highest NA (>95%) against Meloidogyne incognita, both in vitro and in vivo tests, suppressing infections caused by M. enterolobii in tomato crops, too. In open field tests, the endospores of TB197 strain showed a reduction of 81% in the infection severity caused by M. enterolobii (p ≤ 0.05), while the galling index (GI) was reduced 84% (p ≤ 0.05) in tomato greenhouse-tests. Also, a reduction of the root necrosis (81%) caused by Radopholus similis in banana plantations (p ≤ 0.05), compared to the control was observed. Owing to their efficacy in controlling PPNs infections, the endospores and secondary metabolites of B. paralicheniformis TB197 strain could be used in bionematicidal formulations.

Differential Activation of Ferulic Acid Catabolic Pathways of Amycolatopsis sp. ATCC 39116 in Submerged and Surface Cultures.

Amycolatopsis sp. ATCC 39116 catabolizes ferulic acid by the non-oxidative deacetylation and ß-oxidation pathways to produce vanillin and vanillic acid, respectively. In submerged culture, vanillin productivity decreased more than 8-fold, when ferulic, p-coumaric, and caffeic acids were employed in pre-cultures of the microorganism in order to activate the ferulic acid catabolic pathways, resulting in a carbon redistribution since vanillic acid and guaiacol productivities increased more than 5-fold compared with control. In contrast, in surface culture, the effects of ferulic and sinapic acids in pre-cultures were totally opposite to those of the submerged culture, directing the carbon distribution into vanillin formation. In surface culture, more than 30% of ferulic acid can be used as carbon source for other metabolic processes, such as ATP regeneration. In this way, the intracellular ATP concentration remained constant during the biotransformation process by surface culture (100 µg ATP/mg protein), demonstrating a high energetic state, which can maintain active the non-oxidative deacetylation pathway. In contrast, in submerged culture, it decreased 3.15-fold at the end of the biotransformation compared with the initial content, showing a low energetic state, while the NAD+/NADH ratio (23.15) increased 1.81-fold. It seems that in submerged culture, low energetic and high oxidative states are the physiological conditions that can redirect the ferulic catabolism into ß-oxidative pathway and/or vanillin oxidation to produce vanillic acid.

Isolation and Characterization of a New Ferulic-Acid-Biotransforming Bacillus megaterium from Maize Alkaline Wastewater (Nejayote).

Nejayote is an alkaline wastewater generated during the nixtamalization process. Nejayote contains high-value compounds such as ferulic acid (FA), which is widely employed as a substrate for the biotechnological production of flavors and aromas. In the present study, the isolation, identification, and characterization of a native strain of Bacillus megaterium were performed, and its capacity to produce 4-vinylguaiacol (4VG) from ferulic acid was evaluated by employing growing cell and resting cell systems. Growing cells of native B. megaterium biotransformed 6 mM crude FA in nejayote into 2.1 mM 4VG, reaching a productivity of 0.21 mM h-1 4VG, while nejayote enriched with FA at 10, 15, and 25 mM resulted in the formation of 2.4, 3.8, and 6.2 mM 4VG and productivities of 0.24, 0.38, and 0.51 mM h-1 4VG, respectively. In the resting cell system, from 6 and 25 mM pure FA, 3.5 mM 4VG was produced (0.18 mM h-1 4VG), while at 10 and 15 mM FA, 4.6 and 5.1 mM 4VG (average of 0.24 mM h-1 4VG) were obtained, respectively. The native B. megaterium strain, isolated from nejayote, showed great biotechnological potential to produce 4VG from crude FA contained in this wastewater, in which other Bacillus species, such as B. licheniformis and B. cereus, were unable to grow and biotransform FA into 4VG.