BMC Genomics

Oenococcus oeni is a lactic acid bacteria species adapted to the low pH, ethanol-rich environments of wine and cider fermentation, where it performs the crucial role of malolactic fermentation. It has a small genome and has lost the mutS-mutL DNA mismatch repair genes, making it a hypermutable and highly specialized species. Two main lineages of strains, named groups A and B, have been described to date, as well as other subgroups correlated to different types of wines or regions. A third group "C" has also been hypothesized based on sequence analysis, but it remains controversial. In this study we have elucidated the species population structure by sequencing 14 genomes of new strains isolated from cider and kombucha and performing comparative genomics analyses. Sequence-based phylogenetic trees confirmed a population structure of 4 clades: The previously identified A and B, a third group "C" consisting of the new cider strains and a small subgroup of wine strains previously attributed to group B, and a fourth group "D" exclusively represented by kombucha strains. A pair of complete genomes from group C and D were compared to the circularized O. oeni PSU-1 strain reference genome and no genomic rearrangements were found. Phylogenetic trees, K-means clustering and pangenome gene clusters evidenced the existence of smaller, specialized subgroups of strains. Using the pangenome, genomic differences in stress resistance and biosynthetic pathways were found to uniquely distinguish the C and D clades. The obtained results, including the additional cider and kombucha strains, firmly established the O. oeni population structure. Group C does not appear as fully domesticated as group A to wine, but showed several unique patterns which may be due to ongoing specialization to the cider environment. Group D was shown to be the most divergent member of O. oeni to date, appearing as the closest to a pre-domestication state of the species.MICROWINE - Microbial metagenomics and the modern wine industr

Microbial Ecology of French Dry Fermented Sausages and Mycotoxin Risk Evaluation During Storage

Dry fermented sausages are produced worldwide by well-controlled fermentationprocesses involving complex microbiota including many bacterial and fungal species with key technological roles. However, to date, fungal diversity on sausage casings during storage has not been fully described. In this context, we studied the microbial communities from dry fermented sausages naturally colonized or voluntarily surface inoculated with molds during storage using both culture-dependent and metabarcoding methods. Staphylococci and lactic acid bacteria largely dominated in samples, although some halotolerant genera (e.g., Halomonas, Tetragenococcus, and Celerinatantimonas spp.) were also frequently observed. Fungal populations varied from 7.2 to 9.8 log TFU/cm2 sausage casing during storage, suggesting relatively low count variability among products. Fungal diversity identified on voluntarily inoculated casings was lower (dominated by Penicillium nalgiovense and Debaryomyces hansenii) than naturally environment-inoculated fermented sausages (colonized by P. nalgiovense, Penicillium nordicum, and other Penicillium spp. and sporadically by Scopulariopsis sp., D. hansenii, and Candida zeylanoïdes). P. nalgiovense and D. hansenii were systematically identified, highlighting their key technological role. The mycotoxin risk was then evaluated, and in situ mycotoxin production of selected mold isolates was determined during pilot-scale sausage productions. Among the identified fungal species, P. nalgiovense was confirmed not to produce mycotoxins. However, some P. nordicum, Penicillium chrysogenum, Penicillium bialowienzense, Penicillium brevicompactum, and Penicillium citreonigrum isolates produced one or more mycotoxins in vitro. P. nordicum also produced ochratoxin A during pilotscale sausage productions using “worst-case” conditions in the absence of biotic competition. These data provide new knowledge on fermented sausage microbiota and the potential mycotoxin risk during storage

Diversity within Italian Cheesemaking Brine-Associated Bacterial Communities Evidenced by Massive Parallel 16S rRNA Gene Tag Sequencing

This study explored the bacterial diversity of brines used for cheesemaking in Italy, as well as their physicochemical characteristics. In this context, 19 brines used to salt soft, semi-hard, and hard Italian cheeses were collected in 14 commercial cheese plants and analyzed using a culture-independent amplicon sequencing approach in order to describe their bacterial microbiota. Large NaCl concentration variations were observed among the selected brines, with hard cheese brines exhibiting the highest values. Acidity values showed a great variability too, probably in relation to the brine use prior to sampling. Despite their high salt content, brine microbial loads ranged from 2.11 to 6.51 log CFU/mL for the total mesophilic count. Microbial community profiling assessed by 16S rRNA gene sequencing showed that these ecosystems were dominated by Firmicutes and Proteobacteria, followed by Actinobacteria and Bacteroidetes. Cheese type and brine salinity seem to be the main parameters accountable for brine microbial diversity. On the contrary, brine pH, acidity and protein concentration, correlated to cheese brine age, did not have any selective effect on the microbiota composition. Nine major genera were present in all analyzed brines, indicating that they might compose the core microbiome of cheese brines. Staphylococcus aureus was occasionally detected in brines using selective culture media. Interestingly, bacterial genera associated with a functional and technological use were frequently detected. Indeed Bifidobacteriaceae, which might be valuable probiotic candidates, and specific microbial genera such as Tetragenococcus, Corynebacterium and non-pathogenic Staphylococcus, which can contribute to sensorial properties of ripened cheeses, were widespread within brines. \ua9 2017 Marino, Innocente, Maifreni, Mounier, Cobo-D\uedaz, Coton, Carraro and Cardazzo

Duplex PCR method for rapid detection of Zymomonas mobilis in cider

International audienc

Polyphasic study of Zymomonas mobilis strains revealing the existence of a novel subspecies Z. mobilis subsp. francensis subsp. nov., isolated from French cider

International audienceZymomonas mobilis strains recently isolated from French ‘framboisé’ ciders were compared with collection strains of the two defined subspecies, Z. mobilis subsp. mobilis and Z. mobilis subsp. pomaceae, using a polyphasic approach. Six strains isolated from six different regions of France were compared with three strains of Z. mobilis subsp. mobilis, including the type strain LMG 404T, and four strains of Z. mobilis subsp. pomaceae, including the type strain LMG 448T, using phenotypic and genotypic methods. For phenotypic characterization, both physiological tests and SDS-PAGE protein profiles revealed significant differences between the two known subspecies and the French isolates; three distinct groups were observed. These findings were further confirmed by random amplified polymorphic DNA and repetitive extragenic palindromic-PCR genotyping methods in which the French isolates were clearly distinguished from the other two subspecies. Sequence analysis of a fragment ranging from 604 to 617 nucleotides corresponding to the 16S–23S rRNA gene intergenic spacer region (ISR), a 592 nucleotide HSP60 gene fragment and a 1044 nucleotide gyrB gene fragment confirmed the presence of three distinct groups. The French strains exhibited almost 94 % similarity to the ISR, 90 % to HSP60 and 86 % to gyrB sequences of the three collection strains of Z. mobilis subsp. mobilis and 87, 84 and 80 % sequence similarity, respectively, was observed with the four Z. mobilis subsp. pomaceae strains. Based on both the phenotypic and genotypic results, the French strains are proposed to represent a novel subspecies, Zymomonas mobilis subsp. francensis subsp. nov. Strain AN0101T (=LMG 22974T=CIP 108684T) was designated as the type strain

Unraveling microbial ecology of industrial-scale Kombucha fermentations by metabarcoding and culture-based methods.

Kombucha, historically an Asian tea-based fermented drink, has recently become trendy in Western countries. Producers claim it bears health-enhancing properties that may come from the tea or metabolites produced by its microbiome. Despite its long history of production, microbial richness and dynamics have not been fully unraveled, especially at an industrial scale. Moreover, the impact of tea type (green or black) on microbial ecology was not studied. Here, we compared microbial communities from industrial-scale black and green tea fermentations, still traditionally carried out by a microbial biofilm, using culture-dependent and metabarcoding approaches. Dominant bacterial species belonged to Acetobacteraceae and to a lesser extent Lactobacteriaceae, while the main identified yeasts corresponded to Dekkera, Hanseniaspora and Zygosaccharomyces during all fermentations. Species richness decreased over the 8-day fermentation. Among acetic acid bacteria, Gluconacetobacter europaeus, Gluconobacter oxydans, G. saccharivorans and Acetobacter peroxydans emerged as dominant species. The main lactic acid bacteria, Oenococcus oeni, was strongly associated with green tea fermentations. Tea type did not influence yeast community, with Dekkera bruxellensis, D. anomala, Zygosaccharomyces bailii and Hanseniaspora valbyensis as most dominant. This study unraveled a distinctive core microbial community which is essential for fermentation control and could lead to Kombucha quality standardization

Two novel <em>Saccharomycopsis</em> species isolated from black olive brines and a tropical plant. Description of <em>Saccharomycopsis olivae</em> f. a., sp. nov. and <em>Saccharomycopsis guyanensis</em> f. a., sp. nov. Reassignment of <em>Candida amapae</em> to <em>Saccharomycopsis amapae</em> f. a., comb. nov., <em>Candida lassenensis</em> to <em>Saccharomycopsis lassenensis</em> f. a., comb. nov. and <em>Arthroascus babjevae</em> to <em>Saccharomycopsis babjevae</em> f. a., comb. nov.

International audienceThree yeast strains related to members of the genus Saccharomycopsis were isolated. One strain (CUB 1310) was isolated from olive brines of fermented black olives in France and two strains (CUB 1454 and CLIB 1455) were isolated from a plant in French Guiana. Sequence analyses based on the D1/D2 domains of the nuclear large subunit rRNA gene, small-subunit rRNA gene and partial EF-1 alpha gene revealed that the strains represented two novel taxa exhibiting extensive sequence divergence from the previously described species of the genus Saccharomycopsis. Two novel species are described to accommodate these newly isolated strains: Saccharomycopsis olivae sp. nov. (type strain CLIB 1310(T)=CBS 12701(T)) and Saccharomycopsis guyanensis sp. nov. (type strain CLIB 1455(T)= CBS 12914(T) and strain CLIB 1454). Both strains CLIB 1454 and CUB 1455(T) displayed identical sequences but differed in their ability to metabolize sorbitol and in their morphology on agar medium. Candida amapae, Candida lassensensis and Arthroascus babjevae belonging to the Saccharomycopsis clade, are reassigned to Saccharomycopsis as novel combinations

Citeromyces nyonsensis sp. nov., a novel yeast species isolated from black olive brine

A yeast strain was isolated from olive brines in a fermented black olive and olive oil manufacturing plant in the town of Nyons (France). On the basis of domains 1 and 2 (D1/D2) large subunit (LSU) rRNA gene and internal transcribed spacer (ITS) region sequence analyses, the strain CLIB 1303(T) was found to be closely related, but clearly distinct, from the three existing species of the genus Citeromyces: Citeromyces matritensis, Citeromyces siamensis and Citeromyces haiwaiiensis. Strain CLIB 1303(T) exhibited 6 bp, 7 bp and 12 bp divergences in the D1/D2 LSU rRNA gene with C. siamensis, C. matritensis and C. hawaiiensis, respectively. ITS region divergence amounted to more than 8 %, 4 % and 4.5 % with C. siamensis, C. matritensis and C. hawaiiensis, respectively, in addition to several indels. Like C. matritensis and C. siamensis strains, strain CLIB 1303(T) was shown to be halotolerant and osmotolerant. Phenotypically, strain CLIB 1303(T) can be distinguished from other species of the genus Citeromyces by its inability to assimilate trehalose. The strain CLIB 1303(T) (= CBS 12700(T)) was assigned to a novel species, Citeromyces nyonsensis sp. nov

Authenticity and Typicity of Traditional Cheeses: A Review on Geographical Origin Authentication Methods

Food fraud, corresponding to any intentional action to deceive purchasers and gain an undue economical advantage, is estimated to result in a 10 to 65 billion US dollars/year economical cost worldwide. Dairy products, such as cheese, in particular cheeses with protected land- and tradition-related labels, have been listed as among the most impacted as consumers are ready to pay a premium price for traditional and typical products. In this context, efficient food authentication methods are needed to counteract current and emerging frauds. This review reports the available authentication methods, either chemical, physical, or DNA-based methods, currently used for origin authentication, highlighting their principle, reported application to cheese geographical origin authentication, performance, and respective advantages and limits. Isotope and elemental fingerprinting showed consistent accuracy in origin authentication. Other chemical and physical methods, such as near-infrared spectroscopy and nuclear magnetic resonance, require more studies and larger sampling to assess their discriminative power. Emerging DNA-based methods, such as metabarcoding, showed good potential for origin authentication. However, metagenomics, providing a more in-depth view of the cheese microbiota (up to the strain level), but also the combination of methods relying on different targets, can be of interest for this field