Open AccessFunctional Analysis of PilT from the Toxic Cyanobacterium Microcystis aeruginosa PCC 7806
Author(s) -
Kenlee Nakasugi,
Ralitza Alexova,
Charles J. Svenson,
Brett A. Neilan
Publication year - 2007
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.01640-06
Subject(s) - microcystis aeruginosa , biology , microbiology and biotechnology , microcystin , pilus , pseudomonas aeruginosa , microcystis , cyanobacteria , bacteria , gene , genetics , virulence
The evolution of the microcystin toxin gene cluster in phylogenetically distant cyanobacteria has been attributed to recombination, inactivation, and deletion events, although gene transfer may also be involved. Since the microcystin-producingMicrocystis aeruginosa PCC 7806 is naturally transformable, we have initiated the characterization of its type IV pilus system, involved in DNA uptake in many bacteria, to provide a physiological focus for the influence of gene transfer in microcystin evolution. The type IV pilus genespilA ,pilB ,pilC , andpilT were shown to be expressed inM. aeruginosa PCC 7806. The purified PilT protein yielded a maximal ATPase activity of 37.5 ± 1.8 nmol Pi min−1 mg protein−1 , with a requirement for Mg2+ . Heterologous expression indicated that it could complement thepilT mutant ofPseudomonas aeruginosa , but not that of the cyanobacteriumSynechocystis sp. strain PCC 6803, which was unexpected. Differences in two critical residues between theM. aeruginosa PCC 7806 PilT (7806 PilT) and theSynechocystis sp. strain PCC 6803 PilT proteins affected their theoretical structural models, which may explain the nonfunctionality of 7806 PilT in its cyanobacterial counterpart. Screening of thepilT gene in toxic and nontoxic strains ofMicrocystis was also performed.