Detection and sequencing of the microcystin LR-degrading gene,mlrA, from new bacteria isolated from Japanese lakes

Abstract

AbstractmlrA is the only microcystin-degrading gene detected in Sphingomonas sp. MJ-PV. The gene has an extremely rare nucleotide sequence and homologous genes have not yet been discovered in the DNA database. We discovered the existence of a gene homologous to mlrA in new microcystin-degrading bacteria, MD-1 and Y2. These strains possessed mlrA homologues, and the identities of the genes of MD-1 and Y2 with the corresponding MJ-PV exceeded 98% and 84%, respectively. On the other hand, the mlrA gene was not detected in laboratory strains of the closely related Sphingomonas spp. strains employing hemi-nested polymerase chain reaction detection using two primer sets. Although the microcystin-degrading bacteria were closely related strains, they did not cluster together as the same species. We can conclude that the mlrA gene is conserved in three different bacterial species, and it is unique to microcystin degraders but not to the genus Sphingomonas.

High diversity of cultivable heterotrophic bacteria in association with cyanobacterial water blooms

“…Earlier, known strains of bacteria that are able to degrade cyanobacterial toxins are mainly members of the family Sphingomonadaceae within the class Alphaproteobacteria and Paucibacter toxinivorans strains of the class Betaproteobacteria (Jones et al, 1994;Park et al, 2001;Saito et al, 2003;Ishii et al, 2004;Rapala et al, 2005;Amé et al, 2006). The presence of such bacteria in water may have an important role in the natural cleansing of the chemically stable hepatotoxins.…”

Metagenome of microorganisms associated with the toxic Cyanobacteria Microcystis aeruginosa analyzed using the 454 sequencing platform

“…And the microcystin-degrading bacteria, mainly from the Sphingomonadaceae family, degradate the hepatotoxic microcystin produced in the bloom period (Bourne et al, 2001;Harada et al, 2004;Ho et al, 2007;Valeria et al, 2006). We also detected the potentially pathogenic bacteria, Aeromonas, Vibrio, Acinetobacter and Pseudomonas, that may cause adverse health effects in humans and animals (Bourne et al, 2001;Harada et al, 2004;Ho et al, 2007;Ishii et al, 2004;Saito et al, 2003;Valeria et al, 2006). The presence of such pathogens should take into consideration when assessing the risks caused by cyanobacterial blooms.…”

Description of Sphingosinicella xenopeptidilytica sp. nov., a β-peptide-degrading species, and emended descriptions of the genus Sphingosinicella and the species Sphingosinicella microcystinivorans

“…Moreover, a copy of the bapA gene was detected in the genome of Sphingosinicella microcystinivorans Y2 T (Geueke et al, 2006). These observations indicate that utilization of b-peptides distinguishes strain 3-2W4 T and Sphingosinicella microcystinivorans Y2 T from Sphingomonas and Sphingopyxis species.The degradation of microcystin by strain 3-2W4 T was investigated, since this feature is an exceptional trait of Sphingosinicella microcystinivorans (Maruyama et al, 2006; Park et al, 2001;Saito et al, 2003). Strain 3-2W4 T was cultivated in nutrient broth, the cells were harvested in the late-exponential phase by centrifugation and disrupted by ultrasonication and the crude extract was incubated with microcystin-LR, which is the most common type of microcystin.…”

“…The degradation of microcystin by strain 3-2W4 T was investigated, since this feature is an exceptional trait of Sphingosinicella microcystinivorans (Maruyama et al, 2006;Park et al, 2001;Saito et al, 2003). Strain 3-2W4 T was cultivated in nutrient broth, the cells were harvested in the late-exponential phase by centrifugation and disrupted by ultrasonication and the crude extract was incubated with microcystin-LR, which is the most common type of microcystin.…”