An alginate-like exopolysaccharide biosynthesis gene cluster involved in biofilm aerial structure formation by Pseudomonas alkylphenolia.
Pseudomonas alkylphenolia is known to form different types of multicellular structures depending on the environmental stimuli. Aerial structures formed during vapor p-cresol utilization are unique. Transposon mutants that showed a smooth colony phenotype failed to form a differentiated biofilm, including aerial structures and pellicles, and showed deficient surface spreading motility. The transposon insertion sites were located to a gene cluster designated epm (extracellular polymer matrix), which comprises 11 ORFs in the same transcriptional orientation. The putative proteins encoded by the genes in the epm cluster showed amino acid sequence homology to those found in the alginate biosynthesis gene clusters, e.g., in Pseudomonas aeruginosa at similarity levels of 32.3-86.4 %. This overall resemblance indicated that the epm gene cluster encodes proteins that mediate the synthesis of an exopolysaccharide composed of uronic acid(s) similar to alginate. Our preliminary results suggested that the epm-derived polymer is a substituted polymannuronic acid. Gene clusters homologous to the epm gene cluster are found in the genomes of a few species of the genera Pseudomonas, Alcanivorax, and Marinobacter. A mutational analysis showed that the epmJ and epmG genes encoding putative exopolysaccharide-modifying enzymes are required to form multicellular structures. An analysis of the activity of the promoter P epmD using a transcriptional fusion to the green fluorescence protein gene showed that the epm genes are strongly expressed at the tips of the specialized aerial structures. Our results suggested that the epm gene cluster is involved in the formation of a scaffold polysaccharide that is required to form multicellular structures in P. alkylphenolia.
Department of Microbiology and Biomedical Science Institute at CWNU, Changwon National University, Changwon-si, Kyongnam, 641-773, South Korea, klee@changwon.ac.kr.
Kyoung
K
Lee
Eun Jin
EJ
Lim
Keun Soo
KS
Kim
Shir-Ly
SL
Huang
Yaligara
Y
Veeranagouda
Bernd H A
BH
Rehm
D000464:Alginates; D018441:Biofilms / Q000254:growth & development*; D053898:Biosynthetic Pathways / Q000235:genetics*; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D020723:Glucuronic Acid / Q000096:biosynthesis / Q000235:genetics; D006603:Hexuronic Acids; D008969:Molecular Sequence Data; D005810:Multigene Family; D016254:Mutagenesis, Insertional; D016366:Open Reading Frames; D011549:Pseudomonas / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D017422:Sequence Analysis, DNA
D000464:Alginates; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D006603:Hexuronic Acids; D020723:Glucuronic Acid