Molecular characterization of lactic acid populations associated with wine spoilage

Identification and Characterization of Malolactic Bacteria Isolated from the Eastern Foothills of Helan Mountain in China

Malolactic fermentation (MLF) converts malic acid into lactic acid by lactic acid bacteria (LAB). MLF may affect potential wine quality impact as global warming intensifies, and the alcohol in the wine increases, which threatens MLF. Lactiplantibacillus plantarum is considered a new generation of MLF starter because of the ability of high ethanol tolerance and good enological characteristics. In this research, 132 LAB strains were isolated from the eastern foothills of Helan Mountain in Ningxia, China. Twenty-one higher ethanol tolerance isolates were obtained by 15% (v/v) ethanol preliminary screening. They were identified by 16S rRNA sequencing and differentiated by randomly amplified polymorphic DNA (RAPD). Stress factors include ethanol, pH, and SO₂, and the combination of stresses was used to screen stress-tolerance strains. β-D-glucosidase activity, MLF performance, and biogenic amine content were tested to evaluate the enological characteristics. GC-MS detected the volatile components of the wine after MLF. The results showed that twenty strains were identified as L. plantarum, and one strain was Lentilactobacillus hilgardii. Especially, the strains of A7, A18, A23, A50, and B28 showed strong resistance to high ethanol, low pH, and high SO₂. A7, A50, and B28 showed better β-D-glucosidase activity and thus were inoculated into cabernet sauvignon wines whose ethanol content was 14.75% (v/v) to proceed MLF. A7 finished MLF in 36 d, while the control strains Oenococcus oeni 31-DH and L. plantarum BV-S2 finished MLF in 24 d and 28 d, respectively. Nevertheless, A50 and B28 did not finish MLF in 36 d. The data showed that A7 brought a more volatile aroma than control. Notably, the esters and terpenes in the wine increased. These results demonstrated the potential applicability of L. plantarum A7 as a new MLF starter culture, especially for high-ethanol wines.

The diversity of fungal population from grape harvest to young wine in Small Carpathian wine region

The study aimed to identify the filamentous fungi and yeast mycobiota found on the surface and in grapes, grape must, and wine obtained from four red grape varieties: Alibernet, Dornfelder, Blue Frankish, Cabernet Sauvignon, and four white grape varieties: Green Veltliner, Rheinriesling, Pinot Blanc, Sauvignon. Grapes from vineyard Vrbové located in southwestern Slovakia were used for the research in 2020. The identification of filamentous fungi was performed using the macroscopic and microscopic observations and yeasts were identified by MALDI-TOF Mass Spectrometer. A total of 642 isolates were obtained. Grapes were rich in diversity of filamentous fungi (13 genera) and must on yeasts (8 genera). Penicillium, Botrytis, and Hanseniaspora uvarum were identified in both grapes and must. Three of the fungal genera identified by conventional or molecular techniques from the surface of red grape varieties were predominant: Alternaria (26%), Botrytis (21%), and Issatchenkia terricola (13%), two from endogenous mycobiota: Hanseniaspora uvarum (45%) and Botrytis (17%), four from the surface of white grape varieties: Penicillium (25%), Botrytis (21%), Alternaria (16%) and Hanseniaspora uvarum (15%), and three from endogenous mycobiota: Botrytis (44%), Hanseniaspora uvarum (23%) and Alternaria (20%). Saccharomyces cerevisiae, Candida krusei, C. utilis, and Cryptococcus neoformans were identified only in wine.

Evaluation of Malolactic Bacteria Associated with Wines from Albariño Variety as Potential Starters: Screening for Quality and Safety

The biodiversity of lactic acid bacteria in musts and wines of Albariño variety has been studied. The identification of species was addressed through a combination of biochemical and genetic methods (API^® 50 CHL test, 16S rDNA and recA gene sequences, Amplified Ribosomal DNA Restriction Analysis -ARDRA- and 16S-26S intergenic region analysis). The results grouped the isolates into six species predominating those of the genus Lactobacillus and showing a typical biogeographical distribution. Among sixteen strains evaluated, eight of them showed malolactic activity. The study of the presence of genes hdc, odc, and tdc, along with the LC/MS-MS analysis of biogenic amines in wine, showed five strains lacking aminogenic ability. The absence of the pad gene in the above-mentioned strains discards its ability to produce volatile phenols that may adversely affect the aroma. Finally, all malolactic strains showed β-glucosidase activity so that they could contribute to enhance and differentiate the aromatic profile of Albariño wines.

Sub-optimal pH Preadaptation Improves the Survival of Lactobacillus plantarum Strains and the Malic Acid Consumption in Wine-Like Medium

Forty-two oenological strains of Lb. plantarum were assessed for their response to ethanol and pH values generally encountered in wines. Strains showed a higher variability in the survival when exposed to low pH (3.5 or 3.0) than when exposed to ethanol (10 or 14%). The study allowed to individuate the highest ethanol concentration (8%) and the lowest pH value (4.0) for the growth of strains, even if the maximum specific growth rate (μ_max) resulted significantly reduced by these conditions. Two strains (GT1 and LT11) preadapted to 2% ethanol and cultured up to 14% of ethanol showed a higher growth than those non-preadapted when they were cultivated at 8% of ethanol. The evaluation of the same strains preadapted to low pH values (5.0 and 4.0) and then grown at pH 3.5 or 3.0 showed only for GT1 a sensitive μ_max increment when it was cultivated in MRS at pH 3 after a preadaptation to pH 5.0. The survival of GT1 and LT11 was evaluated in Ringer's solution at 14% ethanol after a long-term adaptation in MRS with 2% ethanol or in MRS with 2% ethanol acidified at pH 5.0 (both conditions, BC). Analogously, the survival was evaluated at pH 3.5 after a long-term adaptation in MRS at pH 5.0 or in MRS BC. The impact of the physiologic state (exponential phase vs stationary phase) on the survival was also evaluated. Preadapted cells showed the same behavior of non-preadapted cells only when cultures were recovered in the stationary phase. Mathematical functions were individuated for the description of the survival of GT1 and LT11 in MRS at 14% ethanol or at pH 3.5. Finally, a synthetic wine (SW) was used to assess the behavior of Lb. plantarum GT1 and LT11 preadapted in MRS at 2% ethanol or at pH 5.0 or in BC. Only GT1 preadapted to pH 5.0 and collected in the stationary phase showed constant values of microbial counts after incubation for 15 days at 20°C. In addition, after 15 days the L-malic acid resulted completely degraded and the pH value increased of about 0.3 units.

Probiotic Potential of Pediococcus pentosaceus CRAG3: A New Isolate from Fermented Cucumber

A novel strain of lactic acid bacterium isolated from fermented cucumber was selected due to its high glucansucrase activity. It was identified on the basis of 16S rRNA sequence analysis as Pediococcus pentosaceus CRAG3 (GenBank accession number JX679020). The isolate was round shaped, Gram positive, and catalase negative displaying typical features of lactic acid bacterium. It produced 145 ± 3.27 mg lactic acid per ml of cell-free supernatant. It showed ability to ferment carbohydrates such as sucrose, dextrose, and arabinose; showed resistance to antibiotics such as ciprofloxacin, kanamycin, vancomycin; displayed acid production in triple sugar iron agar test and non-motile nature. Interestingly, the isolate also displayed potential probiotic properties such as hydrophobicity, autoaggregation, coaggregation, and in vitro cell adhesion ability. It exhibited resistance against lysozyme and simulated gastric juice at pH 3.0 with 75 and 58% survival, respectively. It also showed tolerance toward 0.3%, w/v bile salts with 73% survival and ability to deconjugate bile salts. The isolate exhibited antibacterial activity and ability to utilize prebiotics such as inulin and raffinose. These results indicate both probiotic property and glucansucrase-producing ability of P. pentosaceus CRAG3.

Wine fermentation microbiome: a landscape from different Portuguese wine appellations

Grapes and wine musts harbor a complex microbiome, which plays a crucial role in wine fermentation as it impacts on wine flavour and, consequently, on its final quality and value. Unveiling the microbiome and its dynamics, and understanding the ecological factors that explain such biodiversity, has been a challenge to oenology. In this work, we tackle this using a metagenomics approach to describe the natural microbial communities, both fungal and bacterial microorganisms, associated with spontaneous wine fermentations. For this, the wine microbiome, from six Portuguese wine appellations, was fully characterized as regards to three stages of fermentation - Initial Musts (IM), and Start and End of alcoholic fermentations (SF and EF, respectively). The wine fermentation process revealed a higher impact on fungal populations when compared with bacterial communities, and the fermentation evolution clearly caused a loss of the environmental microorganisms. Furthermore, significant differences (p < 0.05) were found in the fungal populations between IM, SF, and EF, and in the bacterial population between IM and SF. Fungal communities were characterized by either the presence of environmental microorganisms and phytopathogens in the IM, or yeasts associated with alcoholic fermentations in wine must samples as Saccharomyces and non-Saccharomyces yeasts (as Lachancea, Metschnikowia, Hanseniaspora, Hyphopichia, Sporothrix, Candida, and Schizosaccharomyces). Among bacterial communities, the most abundant family was Enterobacteriaceae; though families of species associated with the production of lactic acid (Lactobacillaceae, Leuconostocaceae) and acetic acid (Acetobacteriaceae) were also detected. Interestingly, a biogeographical correlation for both fungal and bacterial communities was identified between wine appellations at IM suggesting that each wine region contains specific and embedded microbial communities which may contribute to the uniqueness of regional wines.

Insights into the bacterial community and its temporal succession during the fermentation of wine grapes

Grapes harbor complex microbial communities. It is well known that yeasts, typically Saccharomyces cerevisiae, and bacteria, commonly the lactic acid fermenting Oenococcus oeni, work sequentially during primary and secondary wine fermentation. In addition to these main players, several microbes, often with undesirable effects on wine quality, have been found in grapes and during wine fermentation. However, still little is known about the dynamics of the microbial community during the fermentation process. In previous studies culture dependent methods were applied to detect and identify microbial organisms associated with grapes and grape products, which resulted in a picture that neglected the non-culturable fraction of the microbes. To obtain a more complete picture of how microbial communities change during grape fermentation and how different fermentation techniques might affect the microbial community composition, we employed next-generation sequencing (NGS)—a culture-independent method. A better understanding of the microbial dynamics and their effect on the final product is of great importance to help winemakers produce wine styles of consistent and high quality. In this study, we focused on the bacterial community dynamics during wine vinification by amplifying and sequencing the hypervariable V1–V3 region of the 16S rRNA gene—a phylogenetic marker gene that is ubiquitous within prokaryotes. Bacterial communities and their temporal succession was observed for communities associated with organically and conventionally produced wines. In addition, we analyzed the chemical characteristics of the grape musts during the organic and conventional fermentation process. These analyses revealed distinct bacterial population with specific temporal changes as well as different chemical profiles for the organically and conventionally produced wines. In summary these results suggest a possible correlation between the temporal succession of the bacterial population and the chemical wine profiles.

Biodiversity of Lactobacillus plantarum from traditional Italian wines

In this study, 23 samples of traditional wines produced in Southern Italy were subjected to microbiological analyses with the aim to identify and biotype the predominant species of lactic acid bacilli. For this purpose, a multiple approach, consisting in the application of both phenotypic (API 50CHL test) and biomolecular methods (polymerase chain reaction-denaturing gradient gel electrophoresis and 16S rRNA gene sequencing) was used. The results showed that Lactobacillus plantarum was the predominant species, whereas Lb. brevis was detected in lower amount. In detail, out of 80 isolates 58 were ascribable to Lb. plantarum and 22 to Lb. brevis. Randomly amplified polymorphic DNA-polymerase chain reaction was used to highlight intraspecific variability among Lb. plantarum strains. Interestingly, the cluster analysis evidenced a relationship between different biotypes of Lb. plantarum and their origin, in terms of wine variety. Data acquired in this work show the possibility to obtain several malolactic fermentation starter cultures, composed by different Lb. plantarum biotypes, for their proper use in winemaking processes which are distinctive for each wine.

Antimicrobial activity of pediocin PA-1 against Oenococcus oeni and other wine bacteria

Pediocin PA-1 is an antimicrobial peptide produced by lactic acid bacteria (LAB) that has been sufficiently well characterised to be used in food industry as a biopreservative. Sulphur dioxide is the traditional antimicrobial agent used during the winemaking process to control bacterial growth and wine spoilage. In this study, we describe the effect of pediocin PA-1 alone and in combination with sulphur dioxide and ethanol on the growth of a collection of 53 oenological LAB, 18 acetic acid bacteria and 16 yeast strains; in addition, production of pediocin PA-1 by Pediococcus acidilactici J347-29 in presence of ethanol and grape must is also reported. Inhibitory concentrations (IC) and minimal bactericide concentrations of pediocin PA-1 were determined against LAB, and revealed a bacteriostatic effect. Oenococcus oeni resulted more sensitive to pediocin PA-1 (IC(50) = 19 ng/ml) than the other LAB species (IC(50) = 312 ng/ml). Cooperative inhibitory effects of pediocin PA-1 and either sulphur dioxide or ethanol were observed on LAB growth. Moreover, the pediocin PA-1 producing P. acidilactici strain J347-29 was able to grow and produce the bacteriocin in presence of ethanol (up to 4% ethanol in the fermentation broth) and grape must (up to 80%), which indicated that pediocin PA-1 can be considered as a potential biopreservative in winemaking.

Ecology of indigenous lactic acid bacteria along different winemaking processes of Tempranillo red wine from La Rioja (Spain)

Ecology of the lactic acid bacteria (LAB) during alcoholic fermentation (AF) and spontaneous malolactic fermentation (MLF) of Tempranillo wines from four wineries of La Rioja has been studied analyzing the influence of the winemaking method, processing conditions, and geographical origin. Five different LAB species were isolated during AF, while, during MLF, only Oenococcus oeni was detected. Although the clonal diversity of O. oeni strains was moderate, mixed populations were observed, becoming at least one strain with distinct PFGE profile the main responsible for MLF. Neither the winemaking method nor the cellar situation was correlated with the LAB diversity. However, processing conditions influenced the total number of isolates and the percentage of each isolated species and strains. The winemaking method could cause that genotypes found in semicarbonic maceration did not appear in other wineries. Four genotypes of O. oeni were isolated in more than one of the rest wineries. These four together with other dominant strains might be included in a future selection process.

Dynamics of indigenous lactic acid bacteria populations in wine fermentations from La Rioja (Spain) during three vintages

Diversity of lactic acid bacteria (LAB) species has been analyzed for three consecutive years (2006, 2007, and 2008) during alcoholic and malolactic fermentations of Tempranillo wine in a winery at La Rioja. The results showed differences in malolactic fermentation duration, and in both diversity of LAB species and diversity of Oenococcus oeni genotypes. O. oeni was shown to be the predominant species (73% of total isolates). Monitoring the different strains of O. oeni using pulsed-field gel electrophoresis of chromosomal DNA digested with SfiI and ApaI allowed detection of a total of 37 distinct genotypes, most of them comprised at least two isolates. Six appeared in more than one vintage, one of them being present in the three studied years. Moreover, four genotypes were indistinct of the strains isolated from the air of this same winery in 2007 vintage. The frequency of participation of each genotype varied from year to year, thus dominant genotypes at one year were minority or not present at another year. This suggests that distinct indigenous O. oeni strains are better adapted to the different winery conditions every year. Predominant genotypes that appeared in more than one vintage and lead to quality wines with low histamine contents could be considered as interesting for selecting of new malolactic starter cultures.

Transport of glycerol by Pediococcus pentosaceus isolated from wine

Pediococcus pentosaceus N(5)p is a strain isolated from wine that uses glycerol as its sole carbon source, mainly via the glycerol kinase pathway. The transport of glycerol was investigated in resting cells of this strain. Glycerol uptake followed a Michaelis-Menten relationship with an observed apparent K(m) of 33 microM and a V(max) of 2.5 nmol/min/mg of cell protein. The transport system was specific for glycerol, which was present in the cells grown either on glycerol or glucose suggesting its constitutive nature. The presence of uptake when resting cells were treated with HgCl(2) and the absence of counterflow indicate that facilitated diffusion is not involved in glycerol transport. On the other hand, glycerol uptake was inhibited by the metabolic poisons that affect ATP availability by acting on either electron transport or ATPase activity, and by the proton-conducting uncouplers without any effect on glycerol kinase activity. The restoration of glycerol uptake in de-energized cells by the addition of glucose and low concentration of cyanide-m-chlorophenyl hydrazone was achieved. These results, the first in the genus Pediococcus, provide evidence for an energy-dependent uptake of glycerol that involves the proton motive force directly or coupled with ATP synthesis.

Influence of organic buffers on bacteriocin production by Streptococcus thermophilus ST110

The effect of the organic buffer salts MES, MOPS, and PIPES on the growth of S. thermophilus ST110, medium pH, and accumulation of the antipediococcal bacteriocin thermophilin 110 were evaluated in whey permeate media over a period of 24 h. In nonbuffered medium, thermophilin 110 production at 37 degrees C paralleled the growth of S. thermophilus ST110 and reached a maximum after 8-10 h. Addition of organic buffer salts decreased the drop in medium pH and resulted in increased biomass (dry cells; microg/mL) and higher yields of thermophilin 110 (units/microg cells). The best results were obtained by the addition of 1% (w/v) MES to the medium, which reduced the pH drop to 1.8 units after 10 h of growth (compared to 2.3 pH units in the control) and resulted in a 1.5-fold increase in cell mass (495 microg/mL) and a 7-fold increase in thermophilin 110 yield (77 units/microg dry cells) over the control. The results showed that whey permeate-based media may be suitable for producing large amounts of thermophilin 110 needed for controlling spoilage pediococci in industrial wine and beer fermentations.

In Vivo PCR-DGGE analysis of Lactobacillus plantarum and Oenococcus oeni populations in red wine

In order to monitor Lactobacillus plantarum and Oenococcus oeni in red wine produced with Italian grape (variety "Primitivo di Puglia"), a polymerase chain reaction- denaturing gradient gel electrophoresis (PCR-DGGE) approach using the rpoB as gene target was established. Wine was treated or not with potassium metabisulphite and supplemented with a commercial bacterial starter of O. oeni to encourage malolactic fermentation. Samples were taken from the vinification tanks at 4, 10, 16, 22, and 28 days after the start of alcoholic fermentation. Genomic DNA was directly isolated from wine and identification of lactic acid bacteria was performed using primers rpoB1, rpoB1O, and rpoB2 able to amplify a region of 336 bp corresponding to the rpoB gene. Amplified fragments were separated in a 30-60% DGGE gradient, and the ability of the PCR-DGGE analysis to distinguish L. plantarum and O. oeni was assessed. The results reported suggest that the PCR-DGGE method, based on the rpoB gene as molecular marker, is a reproducible and suitable tool and may be of great value for wine makers in order to monitor spoilage microorganisms during wine fermentation.

Environmental stress response in wine lactic acid bacteria: beyond Bacillus subtilis

Lactic acid bacteria (LAB) constitute a heterogeneous group of bacteria that are traditionally used to produce fermented foods. The industrialization of food transformations has increased the economical importance of LAB, as they play a crucial role in the development of the organoleptic and hygienic quality of fermented products. However, the strains selected for industrial purposes, should tolerate adverse conditions encountered in industrial processes, either during starter handling and storage (freeze-drying, freezing, or spray-drying) or during food processing in which abiotic stresses such as heat, cold, acidity, and high concentration of NaCl or ethanol are common. Wine LAB have to deal with several stresses including an acidic pH, a high alcoholic content, non optimal growth temperatures, and growth-inhibitory compounds such as fatty acids and tannins, originated from yeast and bacteria metabolism. Wine LAB have developed several mechanisms to escape or to tolerate wine conditions. They carry out a malolactic fermentation in this stressful environment. In addition to the regulation of the expression of specific genes, bacteria have evolved adaptive networks to face the challenges of a changing environment and to survive under conditions of stress. The so called Global Regulatory Systems control the simultaneous expression of a large number of genes in response to a variety of environmental stress factors. CIRCE sequences able to bind the HrcA repressor, sigma(B) dependent promoters and CtsR regulatory elements have been observed in several genes identified from wine LAB. Improved knowledge of regulators and a better understanding of LAB stress responses could constitute a basis of comparison with the well known model microorganisms, Escherichia coli and Bacillus subtilis. Moreover, it can provide an important insight into improving current industrial starter strains.

Exploring Lactobacillus plantarum genome diversity by using microarrays

Lactobacillus plantarum is a versatile and flexible species that is encountered in a variety of niches and can utilize a broad range of fermentable carbon sources. To assess if this versatility is linked to a variable gene pool, microarrays containing a subset of small genomic fragments of L. plantarum strain WCFS1 were used to perform stringent genotyping of 20 strains of L. plantarum from various sources. The gene categories with the most genes conserved in all strains were those involved in biosynthesis or degradation of structural compounds like proteins, lipids, and DNA. Conversely, genes involved in sugar transport and catabolism were highly variable between strains. Moreover, besides the obvious regions of variance, like prophages, other regions varied between the strains, including regions encoding plantaricin biosynthesis, nonribosomal peptide biosynthesis, and exopolysaccharide biosynthesis. In many cases, these variable regions colocalized with regions of unusual base composition. Two large regions of flexibility were identified between 2.70 and 2.85 and 3.10 and 3.29 Mb of the WCFS1 chromosome, the latter being close to the origin of replication. The majority of genes encoded in these variable regions are involved in sugar metabolism. This functional overrepresentation and the unusual base composition of these regions led to the hypothesis that they represented lifestyle adaptation regions in L. plantarum. The present study consolidates this hypothesis by showing that there is a high degree of gene content variation among L. plantarum strains in genes located in these regions of the WCFS1 genome. Interestingly, based on our genotyping data L. plantarum strains clustered into two clearly distinguishable groups, which coincided with an earlier proposed subdivision of this species based on conventional methods.

A beta-glucosidase gene isolated from wine Lactobacillus plantarum is regulated by abiotic stresses

AIMS

Little genetic information exists on the ability of wine lactic acid bacteria (LAB) to hydrolyse glycoconjugates during malolactic fermentation. We tried to fill this important gap by characterizing a gene codifying for a putative beta-glucosidase enzyme from wine Lactobacillus plantarum and from a commercial strain of Oenococcus oeni.

METHODS AND RESULTS

The coding region of the putative beta-glucosidase gene is 1400 nucleotides long and started with an ATG codon. The gene is widespread among LAB and the highest identity was observed between the nucleotide of L. plantarum, Lactobacillus pentosus, Lactobacillus paraplantarum and O. oenibeta-glucosidase gene. The protein sequence deduced from the isolated genes has a calculated molecular mass of 61.19 kDa. Furthermore, the expression of the beta-glucosidase gene in L. plantarum strain was analysed, under several stress, by reverse transcriptase (RT)-PCR and Northern-blot analysis. The gene was apparently regulated by abiotic stresses such as temperature, ethanol and pH.

CONCLUSIONS

The beta-glucosidase gene is widespread among LAB and its expression is probably regulated by a wide range of abiotic stresses.

SIGNIFICANCE AND IMPACT OF THE STUDY

The inhibitory effect of temperature and ethanol on the L. plantarumbeta-glucosidase gene may be useful to explain the differences found in beta-glucosidase activity reported in wines by several authors.

Thermophilin 110: a bacteriocin of Streptococcus thermophilus ST110

A screen of thermophilic lactic acid bacteria identified Streptococcus thermophilus strain ST110 as the putative producer of a bacteriocin with high level of activity against pediococci. Thermophilin 110 was isolated from culture supernatant after 16 h of growth and partially purified by a chloroform extraction procedure. The bacteriocin inhibited the growth of several lactic acid bacteria and in the case of Pediococcus acidilactici, it induced cell lysis with the concomitant release of OD260-absorbing material and intracellular enzymes. SDS-PAGE analysis revealed two components with estimated sizes between 4.0 kDa and 4.5 kDa, respectively, with possible involvement in bacteriocin activity as indicated by agar overlay assays with P. acidilactici as the target organism. Thermophilin 110 was inactivated by several proteolytic enzymes and also by alpha-amylase, which indicated the putative requirement of a glycosidic component for activity. The bacteriocin produced by S. thermophilus may be especially useful in the food processing industries to control spoilage caused by pediococci.

Cloning and characterization of the hsp 18.55 gene, a new member of the small heat shock gene family isolated from wine Lactobacillus plantarum

Using a molecular approach based on PCR, RT-PCR and northern blot analysis, a new member of the small heat shock family of wine, Lactobacillus plantarum, was cloned and characterized. The protein sequence deduced from the isolated gene had a calculated molecular mass of 18.548 kDa and was therefore named HSP 18.55. The gene codes for a protein homologous to the previously characterized HSP 19.3 and HSP 18.5 and is co-transcribed with an upstream gene of unknown function. Analysis of the 5' flanking region of the hsp 18.55 gene revealed the presence of putative cis elements able to bind alternative sigma factor sigma(B). Based on its structure, the gene was classified as belonging to class II of the heat shock genes according to Bacillus subtilis nomenclature for shock-responsive genes. Expression of the newly identified small heat shock gene, analyzed by RT-PCR and northern blot analysis, was induced by a wide range of abiotic stresses including heat, cold and ethanol, suggesting that the small family of heat shock genes is probably involved in the general stress response in wine L. plantarum. Moreover, the expression of hsp 18.5, hsp 18.55 and hsp 19.3 genes, analyzed over a complete culture cycle, revealed that early growing cells contained substantial amounts of hsp 18.5, hsp 18.55 and hsp 19.3 mRNAs, which rapidly declined upon entry into stationary phase.

Fast protocols for the 5S rDNA and ITS-2 based identification ofOenococcus oeni

To identify specific marker sequences for the rapid identification of Oenococcus oeni, we sequenced the 23S-5S internal transcribed spacer (ITS-2) region and the 5S rDNA of five different O. oeni strains and three phylogenetically related lactic acid bacteria (LAB). Comparative analysis revealed 100% identity among the ITS-2 region of the O. oeni strains and remarkable differences in length and sequence compared to related LAB. These results enabled us to develop a primer set for a rapid PCR-identification of O. oeni within three hours. Moreover, the comparison of the 5S rDNA sequences and the highly conserved secondary structure provided the template for the design of three fluorescence-labeled specific oligonucleotides for fluorescence in situ hybridization (FISH). These probes are partial complementary to each other. This feature promotes the accessibility to the target sequence within the ribosome and enhances the fluorescence signal. For the rapid identification of Oenococci both the 5S rRNA gene and the ITS-2 region are useful targets.

Cloning, molecular characterization and expression analysis of two small heat shock genes isolated from wine Lactobacillus plantarum

AIM

Understanding the molecular response to stress tolerance of wine Lactobacillus plantarum.

METHODS AND RESULTS

Two genes codifying for heat shock proteins were cloned from wine L. plantarum. The coding regions of the two heat shock genes are 420 and 444 nucleotides long, and started with an ATG codon suggesting that they were translated. The protein sequences deduced from the isolated genes have a molecular mass of 18.483 and 19.282 kDa, respectively, and were therefore named hsp18.5 and hsp19.3. The expression of small heat shock genes was analysed by RT-PCR analysis. Moreover, the 5' and 3' noncoding regions were cloned and sequenced.

CONCLUSIONS

The expression of the heat shock genes was strongly induced by heat, cold and ethanol stress. Analysis of the 5' and 3' flanking regions of hsp18.5 and hsp19.3 genes, revealed the presence of an inverted repeat sequence (TTAGCACTC-N(9)-GAGTGCTAA) homologue to the CIRCE elements found to the upstream regulatory region of heat shock operons, and an inverted sequence that could form a stem and loop structure that it is likely to function as a transcriptional terminator. Based on their structures, the genes were classified as belonging to Class I of heat shock genes according to the B. subtilis nomenclature of heat response genes.

SIGNIFICANCE AND IMPACT OF THE STUDY

Small heat shock genes isolated from wine L. plantarum might have a role in preventing damage by cold stress.