Analysis of Transcriptomic Response to SO₂by Oenococcus oeni Growing in Continuous Culture

Abstract

Malolactic fermentation is an indispensable step in the elaboration of most wines and is generally performed by Oenococcus oeni , a Gram-positive heterofermentative lactic acid bacterium species. While O. oeni is tolerant to many of the wine stresses, including low pH and high ethanol concentrations, it has high sensitivity to SO 2 , an antiseptic and antioxidant compound regularly used in winemaking.

Genomic Analysis of an Excellent Wine-Making Strain Oenococcus oeni SD-2a

“…There are 2,073 ORFs in O. oeni SD-2a, much more than in O. oeni PSU-1of 1701, and a relatively high number among the wholly sequenced O. oeni strains. The ORFs numbers of the other four completed genome sequences of O. oeni strains are between 1858–1970 ( Iglesias et al 2018 ; Lorentzen et al 2019 ; Onetto et al 2021 ). O. oeni SD-2a has six rRNA genes and two copies of 5S-16S-23S rRNA, similar to other sequenced O. oeni strains.…”

“…Indeed, these metabolism-related genes are also the most differentially expressed in wine under different experimental conditions. For example, after ethanol or acid shock, treatment with 5 mg/l SO 2 , or transfer into wine-like medium or non- Saccharomyces -fermented wines, the genes involved in carbohydrate transport and metabolism, amino acid transport and metabolism, and some other metabolisms related genes accounted for the largest proportion in all differentially expressed O. oeni genes ( Costantini et al 2015 ; Olguín et al 2015 ; Margalef-Català et al 2016a ; Liu et al 2017 ; Onetto et al 2021 ; Balmaseda et al 2022 ). It suggests that these metabolisms-related genes are critical for O. oeni strains to survive in the wine environment.…”

“…These proteins can help other proteins to fold normally, prevent their aggregation under stress conditions, or guide protease to degrade denatured proteins (Bech‐Terkilsen et al 2020). In O. oeni strains, the expression level of hsp20 increased significantly after acid shock, ethanol shock (at 8% v/v ethanol condition), combined acid and ethanol shock, or treatments with 5 mg/l SO 2 ( Costantini et al 2015 ; Liu et al 2017 ; Yang et al 2021 ; Onetto et al 2021 ).…”

“…Acid shock leads to the overexpression of Hsp20, malate transport, and malate permease-encoding genes ( Liu et al 2017 ), while the combined acid and ethanol shock increased the expression levels of the recN , recO , mutT genes involved in DNA repair, spermidine and putrescine transport-encoding genes, and the stress-relevant genes hsp20 , clpP , trxA , ctsR , and uspA ( Zhao et al 2020 ; Yang et al 2021 ). Onetto et al (2021) recently characterized the transcriptional response of O. oeni to SO 2. They found that the hsp20 gene and the glutaredoxin protein-encoding gene nrdH were up-regulated at the SO 2 concentration equal to 5 mg/l, while down-regulated genes were involved in transcription regulation, oxidative stress replication, and cell wall assembly.…”

“…Until April 2022, 247 genome sequences of O. oeni strains were available from the National Center for Biotechnology Information (NCBI), and some genome sequences information on different O. oeni strains was analyzed by researchers ( Borneman et al 2010 ; Bridier et al 2010 ; Borneman et al 2012 ; Capozzi et al 2014 ; Dimopoulou et al 2014 ; Lamontanara et al 2014 ; Campbell-Sills et al 2015 ; Jara and Romero 2015 ; Mendoza et al 2015 ; Sternes and Borneman 2016 ; Costantini et al 2020 ). However, only five complete genomes of O. oeni strains have been reported ( Mills et al 2005 ; Iglesias et al 2018 ; Lorentzen et al 2019 ; Onetto et al 2021 ). Overviews of genome sequencing, phylogenetic analyses, and genomic differences among O. oeni strains have been reported, but systematic genomic analyses of specific strains of O. oeni are rare.…”