Analysis of 2,2-DCP degrading bacteria isolated from a paddy field at a rural area in Malang, Indonesia

Aims@#The use of herbicide effectively controls weeds in agricultural practice. However, its release to the surrounding surface water bodies may lead to environmental issues. The aim of this study was to isolate the bacteria that were able to remove 2,2-dichloropropionic acid (2,2-DCP) from a paddy field located in Malang. @*Methodology and results@#The 2,2-DCP degrading bacteria were isolated and their ability to grow on higher 2,2-DCP concentrations (50 and 80 mM) was tested. Bacterial degradation of 2,2-DCP was examined through measurement of released chloride ions. The potential isolates were identified according to their 16S rDNA sequences. Two potential isolates, BB9.2 and BC14.3 were observed for their growth on 20, 50, and 80 mM 2,2-DCP. Isolate BC14.3 had the shortest cell doubling time of approximately 4.1 h with 100% 2,2-DCP (20 mM) utilization, whereas BB9.2 was only able to degrade 80% of 2,2-DCP at the same concentration. The 16S rDNA gene sequences suggested that BB9.2 and BC14.3 belong to Acinetobacter calcoaceticus and Pseudomonas plecoglossicida, respectively. @*Conclusion, significance and impact of study@#Bacterial strains with 2,2-DCP degrading potentials were successfully isolated from long-term exposed agricultural soil. They demonstrated notable utilization of the organic halide. This is the first time that strains of A. calcoaceticus and P. plecoglossicida were reported to utilize 2,2-DCP.

The effectiveness of methanotrophic bacteria and Ochrobactrum anthropi to reduce CH4 and N2O emissions and to promote paddy growth in lowland paddy fields

Aims: Paddy field is one of the sources of greenhouse gasses such as methane (CH4) and nitrous oxide (N2O), which causes global warming and other negative effects in agricultural sector. An alternative to optimize paddy productivity and reduce emissions of CH4 and N2O is by using methanotrophic bacteria and Ochrobactrum anthropi BL2. Methodology and results: This study consisted of two parts, i.e. positive control and experimental treatments. Positive control consisted of 250 kg/ha NPK inorganic fertilizer NPK (15:15:15) (100% of the recommended normal dose) without any methanotrophic bacteria. Meanwhile the experimental treatment consisted of 50 kg/ha inorganic fertilizers NPK (20% of the recommended normal dose) with methanotrophic bacteria (Methylocystis rosea BGM 1, M. parvus BGM 3, Methylococcus capculatus BGM 9, Methylobacter sp. SKM 14) and N2O reducing bacteria (Ochrobactrum anthropi BL2). Using weight indicator of 1000 grams, all the bacteria are capable of increasing paddy productivity by 42.07%, compared to conventional method which can only increase the productivity by 2.51% (Cepy and Wangiyana, 2011). The increasing productivity and growth of paddy plants were due to the nitrogen fixation activity of M. rosea BGM 1, M. capculatus BGM 9, and Methylobacter sp. SKM 14. In the experimental treatment using bacteria, the emission of CH4 and N2O was reduced with the highest CH4 and N2O sinks of 24018.8 mol CH4/day/ha and 68.48 mol N2O/day/ha, respectively. However, the positive control treatment with 100% of the recommended fertilizer dose showed the highest CH4 and N2O emissions which were up to 74346.45 mol CH4/day/ha and 26.21 mol N2O/day/ha, respectively. Conclusion, significance and impact study: All the methanotropic bacteria and O. anthropi BL2 are significantly increase paddy production, compared to positive control treatment. The addition of bacteria in paddy fields results in CH4 and N2O sinks.

The use of rice straw broth as an appropriate medium to isolate purple nonsulfur bacteria from paddy fields

The aims were to explore an appropriate isolating medium for obtaining purple nonsulfur bacteria (PNSB) for use as biofertilizers in saline paddy fields and to obtain pure cultures. We therefore chose a defined isolating medium containing 0.25 percent NaCl, (Glutamate-Acetate broth, GA) and a rice straw broth to compare them for numbers of PNSB obtained, time to obtain pure cultures, diversity and costs. A total of 30 water and 30 sediment samples were collected from saline paddy fields in southern Thailand and used to isolate PNSB in both the isolating media. Based on 60 samples and a period of 13 days incubation under anaerobic light conditions, a greater number of samples produced PNSB growth in GA broth after only day 3; however, after that the rice straw broth provided about a 2 fold increase in the number of samples that produced PNSB growth. Colonies isolated from GA broth required a significantly higher number of repeated streaking to obtain a pure culture (average 3.5) than those from rice straw broth (average 2.7) and the latter medium also produced significantly (P < 0.05) more isolates per sample. Sixty samples of water and sediment, from rice paddies with salinity (average, 3.43 +/- 0.67 mS/cm) and slight acidity (average, pH 5.84 +/- 0.42) provided 62 PNSB isolates by GA broth and 210 isolates by rice straw broth, and rice straw broth also produced a greater prevalence of PNSB. Estimates of the costs based on current prices of media, Gas Pak and electricity to obtain PNSB with the use of GA broth was roughly 6 times higher than for the rice straw broth.

Distribution of Alcohol-tolerant Microfungi in Paddy Field Soils

Ethanol treatment method was attempted for the selective isolation of ethanol-tolerant fungi from two sites of rice paddy fields around Seoul area. The vertical and seasonal fluctuation of the fungal population were also investigated. The ethanoltolerant fungi were Talaromyces stipitatus, T. flavus var. flavus, T. helicus var. major, Eupenicillium javanicum, Emericellopsis terricolor, Pseudourotium zonatum, Aspergillus flavus, Cladosporium cladosporioides, Penicillium frequentans, P. janthinellum, and P. verruculosum. The most dominant species isolated by this method was T. stipitatus. It was found that the numbers of fungal species and colony forming units (CFUs) of ethanol-tolerant fungi were higher in Ascomycota than in Deuteromycota. A particular tendency appeared the highest CFUs in autumn, but lower in spring and winter. T. stipitatus was the dominant species of ethanol tolerant microfungi. This result would suggest that membrane lipid composition of ethanoltolerant fungi isolated from the soils may play on important role in the ethanol tolerance.