The Role of Pseudomonas in Heterotrophic Nitrification: A Case Study on Shrimp Ponds (Litopenaeus vannamei) in Soc Trang Province.

Based on a total of 6,295,650 sequences from the V3 and V4 regions (16S ribosomal RNA), the composition of the microorganism communities in the water of three Litopenaeus vannamei (Decapoda, Whiteleg shrimp; Soc Trang, Vietnam) ponds were identified. Pseudomonas (10-20.29%), Methylophilus (13.26-24.28%), and Flavobacterium (2.6-19.29%) were the most abundant genera. The total ammonia (TAN) concentration (p = 0.025) and temperature (p = 0.015) were significantly correlated with the relative abundance of Pseudomonas in two bacterial communities (ST1, ST4), whereas the predictive functions of microorganism communities based on 16S rRNA gene data was estimated using Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUST), which showed that nitrogen metabolism was significantly negatively correlated (p = 0.049) with TAN concentration. The abundance of Pseudomonas and nitrogen metabolism increased with a decrease in TAN concentration. The correlation between TAN concentration and the abundance of Pseudomonas was followed by the isolation, and heterotrophic nitrifying performance analysis was used to confirm our findings. Six Pseudomonas strains capable of heterotrophic nitrification were isolated from the three water samples and showed a complete reduction of 100 mg/L NH4Cl during a 96-h cultivation. These results indicate the potential of applying Pseudomonas in shrimp ponds for water treatment.

Characterization of a new curtovirus, pepper yellow dwarf virus, from chile pepper and distribution in weed hosts in New Mexico.

Over 4,950 asymptomatic weed samples from more than 20 weed species that are host plants for curtoviruses were collected from ten chile pepper fields in southern New Mexico (NM) during 2003, 2004 and 2005 to identify whether they were infected with curtoviruses and to determine which curtoviruses were distributed in the weed population. Polymerase chain reaction using primers designed to detect a portion of the coat protein (cp) gene were used to detect curtoviruses, and infected plants were further tested for specific curtoviruses using primers designed to detect to a portion of the replication-associated protein (rep) gene. Amplification of the cp gene was successful from 3.7, 1.17, and 1.9% of the weed samples in 2003, 2004, and 2005, respectively. Seventy-three amplicons from those samples were sequenced and compared to well-characterized curtoviruses. Analysis of the rep nucleotide sequences showed that approximately 32.9% of the weed isolates tested were closely related to beet mild curly top virus (BMCTV). Approximately 12.4% were closely related to beet severe curly top virus (BSCTV). The rest of the weed isolates (54.7%), which shared a very high level of nucleotide sequence identity to each other, represent a new curtovirus species. Using eight primers designed for PCR, complete genomes of three curtoviruses isolated from chile pepper samples representing the three groups of curtoviruses in southern New Mexico were sequenced. Comparisons of whole sequences of the genomes revealed that the DG2SW171601 isolate (2,929 nucleotides) was nearly identical to BMCTV-W4 (approximately 98% nucleotide sequence identity). The LRME27601 isolate (2,927 nucleotides) was most closely related to BSCTV (approximately 92% nucleotide sequence identity). The LJN17601 isolate (2,959 nucleotides) shared only from 49.9 to 88.8% nucleotide sequence identity with other well-characterized curtoviruses. Based on the accepted cut-off of 89%, we propose that the LJN17601 isolate is a member of a new curtovirus species. Chile peppers infected with this virus in the field express chlorotic stunting symptoms, so we propose the name pepper yellow dwarf virus (PeYDV). This new curtovirus species may be the result of mutations in the genome and recombination between BMCTV-W4 and BSCTV.

Pesticide poisoning of farm workers-implications of blood test results from Vietnam.

Information on the health impacts of pesticides is quite limited in many developing countries, with many surveys relying solely on farmer self-assessments of their health status. To test the reliability of self-reported data, an acetyl cholinesterase enzyme (AChE) blood test was conducted for 190 rice farmers in the Mekong Delta, Vietnam. Results reveal a high prevalence of pesticide poisoning by organophosphate and carbamate exposure, where over 35% of test subjects experienced acute pesticide poisoning (a reduction of AChE >25%), and 21% chronically poisoned (>66% AChE reduction). Using the medical test results as benchmarks, we find that farmers' self-reported symptoms have very weak associations with actual poisoning. To investigate the possible determinants of pesticide poisoning, a probit model was constructed with pesticide amount, toxicity, training, and the use of protective measures as explanatory variables. The results indicate that although the absolute amount of pesticides used does not increase the probability of poisoning, a 1% increase in the use of highly hazardous pesticides (WHO Ia or Ib) increases the probability of poisoning by 3.9% and an increased use of protective measures decreases the probability of poisoning by 44.3%. We also find significant provincial differences in poisoning incidence after we control for individual factors. The provincial effects highlight the potential importance of negative externalities, and suggest that future research on pesticide-related damage should include information on local water, air and soil contamination.