Identification of the Macromolecular Synthesis Operon ofOenococcus oeni

Abstract

The macromolecular synthesis (MMS) operon and two adjacent genes have been sequenced in the wine bacterium <i>Oenococcus oeni</i>. This bacterium is significant for carrying out malolactic fermentation, which is important for flavor maturation of wine. To grow in wine, <i>O. oeni</i> 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 <i>O. oeni</i> MMS operon has two genes, <i>dnaG</i> and <i>sigA</i>, located ~6 Kbp downstream from <i>rpsU</i>, 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 <i>Lactococcus lactis</i>. 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 <i>orfCE1</i>. The recently annotated <i>O. oeni</i> genome sequence incompletely describes the organization and sequence of the MMS operon. We describe the architecture of the <i>O. oeni</i> MMS operon and its location relative to adjacent genes. Further, we describe and compare the organization, identity, and phylogenetic relationship of the <i>O. oeni</i> MMS to other gram-positive bacteria.