New insight into the nitrogen removal capacity and mechanism of Streptomyces mediolani EM-B2

The utilization of actinomycetes as the bioresources for heterotrophic nitrification and aerobic denitrification is rarely reported due to the lack of work to explore their nitrogen biodegradation capabilities. Streptomyces mediolani EM-B2 belonging to actinomycetes could effectively remove high concentration of multiple nitrogen forms, and the maximum removal rates of ammonium, nitrate and nitrite reached 3.46 mg/(L·h), 1.71 mg/(L·h) and 1.73 mg/(L·h), respectively. Nitrite was preferentially consumed from the simultaneous nitrification and denitrification reaction system. Nitrogen balance analysis uncovered that more than 37% of the initial total nitrogen was converted to nitrogenous gas by aerobic denitrification. Experiments with specific inhibitors of nitrification and denitrification revealed that strain EM-B2 contained ammonia monooxygenase, hydroxylamine oxidoreductase, nitrate reductase and nitrite oxidoreductase, which were successfully expressed and detected as 0.43, 0.59, 0.12 and 0.005 U/mg proteins, respectively. These findings may provide new insights into the actinomycetes for bioremediation of nitrogen pollution wastewater.

Specific enzyme functionalities of Fusarium oxysporum compared to host plants

The genus Fusarium contains some of the most studied and important species of plant pathogens that economically affect world agriculture and horticulture. Fusarium spp. are ubiquitous fungi widely distributed in soil, plants as well as in different organic substrates and are also considered as opportunistic human pathogens. The identification of specific enzymes essential to the metabolism of these fungi is expected to provide molecular targets to control the diseases they induce to their hosts. Through applications of traditional techniques of sequence homology comparison by similarity search and Markov modeling, this report describes the characterization of enzymatic functionalities associated to protein targets that could be considered for the control of root rots induced by Fusarium oxysporum. From the analysis of 318 F. graminearum enzymes, we retrieved 30 enzymes that are specific of F. oxysporum compared to 15 species of host plants. By comparing these 30 specific enzymes of F. oxysporum with the genome of Arabidopsis thaliana, Brassica rapa, Glycine max, Jatropha curcas and Ricinus communis, we found 7 key specific enzymes whose inhibition is expected to affect significantly the development of the fungus and 5 specific enzymes that were considered here to be secondary because they are inserted in pathways with alternative routes.

Nematicidal potential and specific enzyme activity enhancement potential of neem (Azadirachta indica A. Juss.) aerial parts

Nematodes are considered as major plant parasites damaging most of the crops, and neem plant exhibits potential nematicidal and insecticidal properties. This study aimed to check nemato-toxic potential of neem (Azadirachta indica) plant using in vitro and in-planta trials against Meloidogyne incognita. The findings suggested that the neem extracts were lethal to second-stage juvenile (J₂) and egg hatching with simultaneous enhancement in treated tomato plant growth. The egg numbers of M. incognita found less sensitive to the aqueous and alcoholic extracts than those of J₂ as per LC₅₀ values. Complete mortality of J₂s was recorded at 40, 60, and 80% of neem standard extract (SE) dilutions and for undiluted SE of neem. The undiluted SE extract showed 100% inhibition of egg production. The highest reductions in the number of galls/root system, J₂ population, and egg production were observed with 80, 85, and 82% SE as compared control (untreated distilled water). The maximum 250% growth increment was observed in the length of tomato roots supplemented with neem extracts. Resistance-related enzyme [phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POX)] activities in tomato plant have been increased significantly by supplementation with neem extracts. It appears that the aerial parts of neem (A. indica) extracts showed significant and sustainable eco-friendly nemato-toxic potential towards M. incognita growth inhibition and eradication using alcoholic extracts compared to aqueous. From this study, it was concluded that the neem aerial parts were useful for the control of M. incognita and could be a possible replacement for synthetic nematicides in crop protection with utilization in enhancement of specific enzyme activity in tomato plants.