PUL ID

PUL0323

PubMed

28617843, PLoS One. 2017 Jun 15;12(6):e0179761. doi: 10.1371/journal.pone.0179761. eCollection 2017.

Characterization method

fitness contribution assay, insertion sequencing

Genomic accession number

NZ_CP034484.1

Nucelotide position range

3496872-3504872

Substrate

galactan

Loci

ganB- ganA- ganQ- ganP- ganS- ganR

Species

Bacillus subtilis subsp. subtilis/135461

Degradation or Biosynthesis

degradation

Cluster number

1

Gene name

Gene position

Gene type

Found by CGCFinder?

ganB 1 - 1290 (-) CAZyme: CBM61|GH53 Yes
ganA 1370 - 3433 (-) CAZyme: GH42 Yes
ganQ 3452 - 4303 (-) TC: gnl|TC-DB|O07011|3.A.1.1.2 Yes
ganP 4307 - 5563 (-) TC: gnl|TC-DB|O32261|3.A.1.1.2 Yes
ganS 5603 - 6868 (-) TC: gnl|TC-DB|O07009|3.A.1.1.2 Yes
ganR 7009 - 8001 (-) STP: STP|LacI,STP|Peripla_BP_3 No

PUL ID

PUL0323

PubMed

28617843, PLoS One. 2017 Jun 15;12(6):e0179761. doi: 10.1371/journal.pone.0179761. eCollection 2017.

Title

Characterization of the regulation of a plant polysaccharide utilization operon and its role in biofilm formation in Bacillus subtilis.

Author

Habib C, Yu Y, Gozzi K, Ching C, Shemesh M, Chai Y

Abstract

The soil bacterium Bacillus subtilis is often found in association with plants in the rhizosphere. Previously, plant polysaccharides have been shown to stimulate formation of root-associated multicellular communities, or biofilms, in this bacterium, yet the underlying mechanism is not fully understood. A five-gene gan operon (ganSPQAB) in B. subtilis has recently been shown to be involved in utilization of the plant-derived polysaccharide galactan. Despite these findings, molecular details about the regulation of the operon and the role of the operon in biofilm formation remain elusive. In this study, we performed comprehensive genetic analyses on the regulation of the gan operon. We show that this operon is regulated both by a LacI-like transcription repressor (GanR), which directly binds to pairs of inverted DNA repeats in the promoter region of the operon, and by the catabolite control protein A (CcpA). Derepression can be triggered by the presence of the inducer beta-1,4-galactobiose, a hydrolysis product of galactan, or in situ when B. subtilis cells are associated with plant roots. In addition to the transcriptional regulation, the encoded ss-galactosidase GanA (by ganA), which hydrolyzes ss-1,4-galactobiose into galactose, is inhibited at the enzymatic level by the catalytic product galactose. Thus, the galactan utilization pathway is under complex regulation involving both positive and negative feedback mechanisms in B. subtilis. We discuss about the biological significance of such complex regulation as well as a hypothesis of biofilm induction by galactan via multiple mechanisms.