Conference
FUNCTIONAL ANALYSIS OF THE BCEA GENE OF THE BURKHOLDERIA CEPACIA EXOPOLYSACCHARIDE BIOSYNTHETIC CLUSTER
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— 2008
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December 2008
Abstract
Cepacian is an exopolysaccharide (EPS) produced by bacteria of the Burkholderia cepacia complex (BCC), important human opportunistic pathogens, particularly among Cystic Fibrosis (CF) patients. It is composed of a repeating unit with Dglucose, D-rhamnose, D-mannose, D-galactose and D-glucuronic acid in the ratio 1:1:1:3:1 [1].This EPS is thought to play a role in virulence and persistence in BCC infections [2]. The bceA gene of the Burkholderia cepacia IST408 EPS biosynthetic cluster [3] encodes a 55.3 kDa bifunctional protein, with phosphomannose isomerase (PMI) and GDP-mannose pyrophosphorylase (GMP) activities (type II PMI family). The GMP activity of BceA is strongly dependent on the presence of Ca2+ or Mn2+, while the PMI activity can use a broader variety of divalent cations (Ca2+> Mn2+>Mg2+>Co2+>Ni2+). The lack of a functional BceA, in a non-polar bceA mutant, had no effect on the amounts of EPS produced, although the viscosity of aqueous solutions prepared with the mutant biopolymer was significantly below that registered for the wild-type cepacian. This bceA mutant formed biofilms with a size 6-fold below the size of the wild-type biofilms. The efficiency of B. cepacia IST408 to kill the nematode model of infection Caenorhabditis elegans was not affected in the absence of BceA. An in silico search for putative bceA homologues within available genome sequences from 11 strains of the Burkholderia genus revealed the presence in their genomes of 2 to 5 bceA ortologues. This bioinformatics analysis, together with other experimental evidences, indicates that bceA is not essential for EPS production because additional bceA functional homologues may be encoded in the genome sequence B. cepacia IST408. Due to low amino acid identity between BceA and the BceA homologues examined and the human PMI, these proteins might be potential therapeutic targets to tackle infections caused by BCC, particularly among cystic fibrosis patients. Supported by FCT (POCTI/BIO/38273/2001). [1] Richau JA et al. (2000) J Clin Microbiol 40:1651-1655 [2] Moreira LM et al. (2003) Biochem Biophys Res Commun 312:323-333 [3] Cunha MV et al. (2004) J Clin Microbiol 42:3052-3058
Publication details
Authors in the community:
Isabel Sá-Correia
ist11177
Jorge Humberto Gomes Leitão
ist14034
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Location of the conference
Aveiro, Portugal
Fields of Science and Technology (FOS)
biological-sciences - Biological sciences
Publication language (ISO code)
eng - English
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