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July 2016 WINES&VINES 39 PRACTICAL WINERY & VINEYARD WINEMAKING etc. The synthesis and activity of these stress proteins is controlled by genes and their regulators. Understanding genomes of LAB strains with different enological per- formance should help researchers deter- mine the genetic causes. A global comparison of genomes is required to understand the difference between strains. Initial genetic research on stress response uti- lized subtractive hybridization, a technique used to compare two DNA populations of a small number of wine LAB strains. 4,11 Certain genes and genomic regions were statistically more numerous in strains more resistant to stress. 26 Subsequently, the advent of high-speed se- quencing methods has been able to provide us with access to a greater number of genomes. According to A.R. Borneman et al., 5 the variation in the genomes of 14 strains exam- ined for stress response can be explained by such factors as a prophage (a bacterial virus incorporated into its DNA), regions involved with the utilization and transport of sugars and regions responsible for the biosynthesis of amino acids and cell wall components. De- pending on the bacterial strain, these genetic regions may not be transcribed and translated into proteins during the stress response, or they may be transcribed and translated, but not with the same intensity. Measuring the level of transcription of the genes identified by subtractive hybridization has shown that even when faced with the same stress, not all bacterial strains use the same set of genes. 11 In this work, four wine LAB strains chosen for their opposite response to pH and ethanol were analyzed. All previ- ously known genes for O. oeni (pan-genome), more than 2,600, were hybridized with RNA extracted from the wine LAB strains inocu- lated into wine, and the level of gene expres- sion was measured. The regions linked to the cell's ability to interact with its environment, synthesize cell wall compounds, accomplish DNA repair and transport sugar were over-expressed, while areas linked to the modification and synthe- sis of proteins were under-expressed. 16 The genes whose expression varies are not the same genes expressed when the bacteria is inoculated into another wine with the same pH and alcohol. 7 Thus, the range of genes used in stress response varies with the strain and with the wine. This result is confirmed in transcrip- tion profiles (such as the presence/absence of transcripts) for several strains inoculated into different wines. 22 This shows the importance of the wine matrix in gene expression. The proteomic approach, which describes all the proteins present at a particular point in time, is another strategy that became avail- able through progress in the global analysis of cell and membrane proteins. This approach indicates the state of cell functioning in rela- tion to the pathways used to cope with changes in the environment. Global protein analysis is necessary to identify the networks of associated functions. The comparison of proteins produced by wine LAB under normal or stress conditions could identify the genes responsible for stress responses. This strategy could be de- veloped as the analysis protocols are de- scribed for O. oeni. 24,25 Differences between proteomes of a selected wine LAB culture before and after inoculation into wine pro- vides some interesting directions. 9 Trends and expectations for selected LAB starters There is no doubt the most important quality of a selected wine LAB starter culture is its capacity to degrade all of the L-malic acid as rapidly as possible, but the sensory impact on the wine is also important. Wine LAB possess glycosidase enzymes capable of lib- erating varietal aroma precursors into the media. 12,23 Even if it were possible to express this activity in recombinant bacteria or yeast, it is more realistic to utilize strain selection Sanitary Stainless Welding Inc. is the exclusive North American distributor for the Marzola product line