Project description:Mostly, lactic acid bacteria (LAB), including food-spoilage-associated, grow in communities consisting of several microbial species. The interspecies interactions eventually shape the structure and global activity of a given microbial community. Generally, the knowledge on system level responses of LAB (especially food-spoilage-associated) during such interactions is very limited. To study transcriptome responses during interactions between three MAP meat-spoilage-associated LAB (Leuconostoc gelidum subsp. gasicomitatum LMG 18811T, Lactococcus piscium MKFS47 and Lactobacillus oligofermentans LMG 22743T) we grew them separately in individual cultures and in mixed cultures pairwise (three combinations) and all together (triple culture) in three replicates on a glucose-containing growth medium (MRS) under microaerobic conditions at 25 C, samples were taken at three time points (3, 5 and 11 h) and extracted RNA were sequenced. The experiments were performed in two batches. At first (batch 1), co-cultivation of Le. gelidum and Lc. piscium accompanied with their individual cultures was performed and processed. The raw RNA-seq data for the individual culture of Lc. piscium from the batch 1 were uploaded earlier and are available in the ArrayExpress database under accession number E-MTAB-3245. Later (batch 2), two other pairwise cultures (Le. gelidum + Lb. oligofermentans and Lc. piscium + Lb. oligofermentans) and the triple culture were grown together with the individual cultures of all three LAB. Designations used for the sample names: G: Le. gelidum; P: Lc. piscium; O: Lb. oligofermentans; GO, PO, PG: pairwise cultures of the corresponding species; OPG: triple culture; b1: batch 1; b2: batch 2. Example: 3G2_b1: 3 h, Le. gelidum, 2nd replicate, batch 1; 11PO3_b2: 11 h, pairwise culture of Lc. piscium and Lb. oligofermentans, 3d replicate, batch 2. One sample (5PO3_b2) had very low number of reads ~ 9000, and, therefore, was not uploaded under this project. RNA extraction and library construction were done analogously as in the study (Andreevskaya M et al., 2015. Appl. Environ. Microbiol. 81:38003811, doi: 10.1128/AEM.00320-15). Ribosomal RNA was omitted. Libraries were sequenced in five lanes using SOLiD 5500XL (Life technologies, Foster City, Ca, USA) to produce 75 bp single-end reads. For the data submission, xsq files obtained from SOLiD 5500XL machine, were converted into fastq files. Adapter sequences were removed using cutadapt 1.4.1.

Project description:Raw sausages are perishable foodstuffs; reducing their salt content raises questions about a possible increased spoilage of these products. In this study, we evaluated the influence of salt reduction (from 2.0% to 1.5% [wt/wt]), in combination with two types of packaging (modified atmosphere [50% mix of CO2-N2] and vacuum packaging), on the onset of spoilage and on the diversity of spoilage-associated bacteria. After 21 days of storage at 8°C, spoilage was easily observed, characterized by noticeable graying of the products and the production of gas and off-odors defined as rancid, sulfurous, or sour. At least one of these types of spoilage occurred in each sample, and the global spoilage intensity was more pronounced in samples stored under modified atmosphere than under vacuum packaging and in samples with the lower salt content. Metagenetic 16S rRNA pyrosequencing revealed that vacuum-packaged samples contained a higher total bacterial richness (n = 69 operational taxonomic units [OTUs]) than samples under the other packaging condition (n = 46 OTUs). The core community was composed of 6 OTUs (Lactobacillus sakei, Lactococcus piscium, Carnobacterium divergens, Carnobacterium maltaromaticum, Serratia proteamaculans, and Brochothrix thermosphacta), whereas 13 OTUs taxonomically assigned to the Enterobacteriaceae, Enterococcaceae, and Leuconostocaceae families comprised a less-abundant subpopulation. This subdominant community was significantly more abundant when 2.0% salt and vacuum packaging were used, and this correlated with a lower degree of spoilage. Our results demonstrate that salt reduction, particularly when it is combined with CO2-enriched packaging, promotes faster spoilage of raw sausages by lowering the overall bacterial diversity (both richness and evenness).Our study takes place in the context of raw meat product manufacturing and is linked to a requirement for salt reduction. Health guidelines are calling for a reduction in dietary salt intake. However, salt has been used for a very long time as a hurdle technology, and salt reduction in meat products raises the question of spoilage and waste of food. The study was conceived to assess the role of sodium chloride reduction in meat products, both at the level of spoilage development and at the level of bacterial diversity, using 16S rRNA amplicon sequencing and raw pork sausage as a meat model.

Dataset Information

Sausages spoilage

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