Identification of the Macromolecular Synthesis Operon of Oenococcus oeni

Abstract

The macromolecular synthesis (MMS) operon and two adjacent genes have been sequenced in the wine bacterium Oenococcus oeni. This bacterium is significant for carrying out malolactic fermentation, which is important for flavor maturation of wine. To grow in wine, O. oeni must adapt to low pH (3.0 to 4.0) and ethanol concentrations as high as 16% (v/v). Understanding the regulation of this key operon will enable improvements in starter culture preparation to ensure successful malolactic fermentation. Preliminary analysis has identified several characteristics emblematic of the typical gram-positive MMS operon and has revealed significant differences from bacteria within closely related genera. The O. oeni MMS operon has two genes, dnaG and sigA, located ~6 Kbp downstream from rpsU, the third gene of the MMS operon. They are encoded by a 3.3 kb genome segment ending with a putative stem-loop transcriptional termination structure most similar to that of Lactococcus lactis. A conserved open-reading-frame with identity to genes in other gram-positive bacteria is located downstream of the primary sigma factor and is here named orfCE1. The recently annotated O. oeni genome sequence incompletely describes the organization and sequence of the MMS operon. We describe the architecture of the O. oeni MMS operon and its location relative to adjacent genes. Further, we describe and compare the organization, identity, and phylogenetic relationship of the O. oeni MMS to other gram-positive bacteria.