Antimicrobial profile of Arthrobacter kerguelensis VL-RK_09 isolated from Mango orchards

Abstract An actinobacterial strain VL-RK_09 having potential antimicrobial activities was isolated from a mango orchard in Krishna District, Andhra Pradesh (India) and was identified as Arthrobacter kerguelensis. The strain A. kerguelensis VL-RK_09 exhibited a broad spectrum of in vitro antimicrobial activity against bacteria and fungi. Production of bioactive metabolites by the strain was the highest in modified yeast extract malt extract dextrose broth, as compared to other media tested. Lactose (1%) and peptone (0.5%) were found to be the most suitable carbon and nitrogen sources, respectively, for the optimum production of the bioactive metabolites. The maximum production of the bioactive metabolites was detected in the culture medium with an initial pH of 7, in which the strain was incubated for five days at 30 °C under shaking conditions. Screening of secondary metabolites obtained from the culture broth led to the isolation of a compound active against a wide variety of Gram-positive and negative bacteria and fungi. The structure of the first active fraction was elucidated using Fourier transform infrared spectroscopy, electrospray ionization mass spectrometry, 1H and 13C nuclear magnetic resonance spectroscopy. The compound was identified as S,S-dipropyl carbonodithioate. This study is the first report of the occurrence of this compound in the genus Arthrobacter.

La bacteria Arthrobacter agilis UMCV2 y diversas aminas inhiben el crecimiento in vitro de hongos destructores de madera / Bacterium Arthrobacter agilis UMCV2 and diverse amines inhibit in vitro growth of wood-decay fungi

El reino Fungi está representado por innumerable cantidad de organismos entre los cuales se encuentran hongos patógenos que deterioran los principales componentes estructurales de la madera, como celulosa, hemicelulosa y lignina. El objetivo de nuestro trabajo fue caracterizar la actividad antifúngica y la producción de diversas aminas de Arthrobacter agilis UMCV2 con acción antagónica sobre hongos xilófagos. Para ello, se aislaron 4 organismos fúngicos (designados en conjunto UMTM) a partir de madera en descomposición en un bosque de pino encino de la comunidad de Cuanajo, Michoacán, México. Dos de ellos presentaron una clara actividad enzimática de celulasas, xilanasas y enzimas accesorias óxido-reductoras, y fueron identificados como pertenecientes a 2 géneros agresivos para la madera: Hypocrea (aislado UMTM3) y Fusarium (aislado UMTM13). In vitro, las aminas evaluadas mostraron tener efecto inhibitorio sobre el crecimiento de los UMTM y la dimetilhexadecilamina; uno de estos compuestos mostró un fuerte potencial para ser utilizado como tratamiento preventivo contra el ataque de hongos destructores de madera.

The kingdom Fungi is represented by a large number of organisms, including pathogens that deteriorate the main structural components of wood, such as cellulose, hemicellulose and lignin. The aim of our work was to characterize the antifungal activity in Arthrobacter agilis UMCV2 and diverse amines against wood-decaying fungi. Four fungal organisms (designated as UMTM) were isolated from decaying wood samples obtained from a forest in Cuanajo-Michoacán, México. Two of them showed a clear enzymatic activity of cellulases, xylanases and oxido-reducing enzymes and were identified as Hypocrea (UMTM3 isolate) and Fusarium (UMTM13 isolate). In vitro, the amines showed inhibitory effect against UMTM growth and one of the amines, dimethylhexadecylamine (DMA16), exhibited strong potential as wood preventive treatment, against the attack of decaying fungi.

Optimization of physical parameters for lipase production from Arthrobacter sp. BGCC#490.

The physical parameters for the production of thermostable, alkaline lipase from Arthrobacter sp. BGCC# 490 were optimized using response surface methodology (RSM), employing face centered central composite design (FCCCD). The design was employed by selecting pH, temperature and incubation period as the model factors and to achieve maximum yield, interaction of these factors was studied by RSM. A second-order quadratic model and response surface method showed that the optimum conditions for lipase production (pH 10.0, temperature 40oC and incubation period 48 h) resulted in 1.6-fold increase in lipase production (13.75 EUml-1), as compared to the initial level (8.6 EUml-1) after 48 h of incubation, whereas its value predicted by the quadratic model was 12.8 EUml-1. Lipase showed stability in the pH range 8-10 and temperature range 40-60oC, with maximum activity at pH 9.0 and temperature 50oC. Lipase activity was enhanced in the presence of K+, Ca2+ and Mg2+ ions, but inhibited by Hg2+ ions. The enzyme exhibited high activity in the presence of acetone, isopropanol and ethanol, but was unaffected by methanol. These properties suggest that the lipase may find potential applications in the detergent industry. The present work also demonstrated the feasibility of using experimental design tools to optimize physical parameters for lipase production by an indigenous Arthrobacter sp.

Microbial Decomposition of alpha-Picoline.

An organism, which degrades alpha-picoline but also utilizes 2-ethylpyridine or piperidine as alternative growth substrates, has been isolated from soil and characterized as arthrobacter sp. alpha-picoline-grown cells oxidize 2-ethylpyridine and vice versa. Other pyridine derivatives tested are neither utilized as growth substrates nor oxidized by the organism. alpha-Picolinate and 2-hydroxy-6-methylpyridine are not metabolized, indicating that degradation is neither initiated by methyl oxidation nor by hydroxylation in the 6-position of pyridine ring. Succinate semi-aldehyde and pyruvate accumulate when alpha-picoline oxidation by resting cell suspensions is blocked by semicarbazide. The Arthrobacter grown on alpha-picoline rapidly oxidizes succinate semi aldehyde...