Molecular characterization of 'Candidatus Liberibacter' species/strains causing huanglongbing disease of citrus in Kenya

This study was undertaken to characterize the alpha subgroup of the proteobacteria causing the huanglongbing (HLB) disease of citrus from three different ecological zones of Kenya namely the Lower highlands (LH2, LH3, 1800-1900 m above sea level); Upper midlands (UM3, UM4, 1390-1475m), Lower midlands (LM5, LM4, LM3 of 1290-1340-1390m), by isolation and sequencing DNA encoding the L10 and L12 ribosomal proteins and the intergenic region. A 7I6-basepair DNA fragment was amplified and sequenced and consisted of 536 basepairs of DNA encoding the L10 protein, 44 basepairs of DNA intergenic region and 136 basepairs of DNA that partially encodes the L12 protein. Sequences of rpL10/L12 protein genes from Kenyan strains were 98 percent and 81 percent similar to the South African 'Candidatus Liberibacter africanus strain Nelspruit' and the Asian 'Candidatus Liberibacter asiaticus' strains, respectively. The intergenic rDNA sequence of Kenyan strain from UM and LM showed 84 percent similarity with 'Candidatus L. africanus strain Nelspruit' and 50 percent similarity with 'Candidatus L. asiaticus' strain. However, the LH strain had an 11- basepairs deletion, while the LM4 had a 5-basepair deletion in the intergenic region compared to 'Candidatus L. africanus strain Nelspruit'. The L10 amino acid sequence was 100 percent homologous among HLB bacteria obtained from the agro-ecological zones in Kenya and the L10 protein sequence was also homologus to 'Candidatus L. africanus strain Nelspruit'. Nevertheless, the L10 amino acid sequence of 'Candidatus L. asiaticus' and the 'Candidatus L. africanus subsp. capensis' differed from the Kenyan strains by 18.36 percent and 11.82 percent, respectively. Phylogenetic analysis of both the L10/L12 rDNA sequences and the L10 amino acid sequences clustered the Kenyan strains of the 'Candidatus Liberibacter' species with members of alpha subdivision of proteobacteria.

Xenobiotics enhance laccase activity in alkali-tolerant gama-proteobacterium JB / Xenobióticos aumentam a atividade de lacase em gama-Proteobacterium JB alcali-tolerante

Various genotoxic textile dyes, xenobiotics, substrates (10 µM) and agrochemicals (100 µg/ml) were tested for enhancement of alkalophilic laccase activity inã-proteobacterium JB. Neutral Red, Indigo Carmine, Naphthol Base Bordears and Sulphast Ruby dyes increased the activity by 3.7, 2.7, 2.6 and 2.3 fold respectively. Xenobiotics/substrates like p-toluidine, 8-hydroxyquinoline and anthracine increased it by 3.4, 2.8 and 2.3 fold respectively. Atrazine and trycyclozole pesticides enhanced the activityby 1.95 and 1.5 fold respectively.

Vários corantes têxteis genotóxicos, xenobióticos, substratos (10 mM) e agroquímicos (100 mM/mL) foram testados quanto ao aumento da atividade de lacase em ã-Proteobacterium JB. Os corantes Neutral Red, Indigo Carmine, Naphtol Base Bordears e Sulphast Ruby aumentaram a atividade em 3,7, 2,7, 2,6 e 2,3 vezes, respectivamente. Xenobióticos/substratos como p-toluidina, 8-hidroxiquinolina e antracina aumentaram a atividade em 3,4, 2,8 e 2,3 vezes, respectivamente. Atrazina e pesticidas triciclozol aumentaram a atividade em 1,95 e 1,5 vezes, respectivamente.

Novel s-triazine-degrading bacteria isolated from agricultural soils of central Chile for herbicide bioremediation

s-Triazine-degrading bacterial strains were isolated from long-term simazine-treated agricultural soils of central Chile. The number of culturable heterotrophic bacteria of these agricultural soils (7 x 10(6) CFU/g of dry soil) was not affected by simazine application on field. The simazine-degrading bacterial strains P51, P52 and C53 were isolated by enrichment in minimal medium using simazine as the sole nitrogen source. Resting cells of strains P51 and P52 degraded >80 percent of simazine within 48 hrs, whereas strain C53 was able to remove >60 percent of the herbicide. The atzA and atzD genes of the s-triazine upper and lower catabolic pathways were detected in strains P51 and C53, while only atzD gene was observed in strain P52. To compare the bacterial 16S rRNA gene sequence structure, ARDRA were performed using the restriction enzymes Msp1 and Hha1. ARDRA indicated that strain P52 was a different ribotype than C53 and P51 strains. For further characterization the novel isolates were identified by 16S rRNA gene sequencing. Strains C53 and P51 belong to the genus Stenotrophomonas and the strain P52 belongs to the genus Arthrobacter . s -Triazine-degrading bacterial strains isolated from contaminated soils could be used as biocatalysts for bioremediation of these herbicides.