Affiliation:
1. Laboratory of Bioinformatics and Genome Biology, Andrés Bello University, and Millennium Institute of Fundamental and Applied Biology
2. Program of Cellular & Molecular Biology, University of Chile, Santiago, Chile
Abstract
ABSTRACT
A cluster of five genes, proposed to be involved in the formation of extracellular polysaccharide (EPS) precursors via the Leloir pathway, have been identified in the acidophilic autotroph
Acidithiobacillus ferrooxidans
. The order of the genes is
luxA-galE-galK-pgm-galM
, encoding a LuxA-like protein, UDP-glucose 4-epimerase, galactokinase, phosphoglucomutase, and galactose mutarotase, respectively. The
gal
cluster forms a single transcriptional unit and is therefore an operon. Two other putative genes of the Leloir pathway,
galU
, potentially encoding UDP-glucose pyrophosphorylase, and a gene designated
galT-like
, which may encode a galactose-1-phosphate uridylyltransferase-like activity, were found unlinked in the genome. Using semiquantitative reverse transcription-PCR, the genes of the
gal
operon were shown to be expressed more during growth in iron medium than in growth in sulfur medium. The functions of
galE
,
pgm
,
galU
, and the
galT-like
gene were validated by complementation of
Escherichia coli
mutants and by in vitro enzyme assays. The data suggest that
A. ferrooxidans
is capable of synthesizing the EPS precursors UDP-glucose and UDP-galactose. In addition, genes
rfbA
, -
B
, -
C
, and -
D
were identified in the genome of
A. ferrooxidans
, suggesting that it can also synthesize the EPS precursor dTDP-rhamnose. Since EPSs constitute the major bulk of biofilms, this study may provide an initial model for the metabolic pathways involved in biofilm formation in
A. ferrooxidans
and aid in understanding the role of biofilms in mineral leaching and the formation of acid mine drainage.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
102 articles.
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