Genome Analysis of the Meat Starter Culture BacteriumStaphylococcus carnosusTM300

Abstract

The Staphylococcus carnosus genome has the highest GC content of all sequenced staphylococcal genomes, with 34.6%, and therefore represents a species that is set apart from S. aureus, S. epidermidis, S. saprophyticus, and S. haemolyticus. With only 2.56 Mbp, the genome belongs to a family of smaller staphylococcal genomes, and the ori and ter regions are asymmetrically arranged with the replichores I (1.05 Mbp) and II (1.5 Mbp). The events leading up to this asymmetry probably occurred not that long ago in evolution, as there was not enough time to approach the natural tendency of a physical balance. Unlike the genomes of pathogenic species, the TM300 genome does not contain mobile elements such as plasmids, insertion sequences, transposons, or STAR elements; also, the number of repeat sequences is markedly decreased, suggesting a comparatively high stability of the genome. While most S. aureus genomes contain several prophages and genomic islands, the TM300 genome contains only one prophage, ⌽TM300, and one genomic island, SCA1, which is characterized by a mosaic structure mainly composed of species-specific genes. Most of the metabolic core pathways are present in the genome. Some open reading frames are truncated, which reflects the nutrient-rich environment of the meat starter culture, making some functions dispensable. The genome is well equipped with all functions necessary for the starter culture, such as nitrate/nitrite reduction, various sugar degradation pathways, two catalases, and nine osmoprotection systems. The genome lacks most of the toxins typical of S. aureus as well as genes involved in biofilm formation, underscoring the nonpathogenic status.It has been known for a long time that staphylococci play a role in the fermentation of dry sausage (52). At first, they were regarded as micrococci, but it turned out that these micrococci were wrongly classified and were in fact staphylococci. Based on DNA/DNA hybridization, biochemical properties, and cell wall composition, these staphylococci formed a new species, which was named Staphylococcus carnosus because the bacteria can be isolated from meat fermentation products and have been used since the 1950s as a starter culture (64).One of the main advantages of starter cultures in fermentedfood processing is that the fermentation and ripening process can be carried out under controlled conditions. In this way, food poisoning and food spoilage microorganisms can be suppressed, and the course of the fermentation process and its termination can be more reliably monitored. During the ripening process of dry sausage, S. carnosus exerts several desired functions (5, 14, 40). First, S. carnosus gradually reduces nitrate to nitrite (50). The advantages of this reaction are that the nitrate concentration is lowered and that nitrite can combine with myoglobin to form nitrosomyoglobin, which results in the typical red color. In the second step, nitrite is then further reduced to ammonia, thus lowering the unbound nitrite concentration (51). Other advantages are d...

Lipoproteins of Gram-Positive Bacteria: Key Players in the Immune Response and Virulence

“…This island is not found in coagulase-negative species such as Staphylococcus carnosus (48). The genetic organization of Sa␣ is highly conserved and is composed of two gene clusters: one cluster carries a number of highly homologous exotoxin-encoding genes (set), and the other one encodes lipoproteins, referred to as lipoprotein-like (lpl), with a typical lipobox-containing signal sequence (49).…”

The Use of Starter Cultures in Traditional Meat Products

“…Genomes of several strains of starter CNS have also been published, namely, S. xylosus SMQ-121 [180], S. xylosus S04002 [181], and S. carnosus TM300 [182].…”

“…carnosus TM300 genome has the highest GC content of all sequenced staphylococcal genomes [182]. It contains only one prophage and one genomic island characterised by a mosaic structure composed of species-specific genes.…”

“…All starter cultures features, such as nitrate/nitrite reduction, several sugar degradation pathways, two catalases, and nine osmoprotection systems, are present. It lacks most virulence factors, namely, the typical S. aureus toxins, as well as biofilm formation genes, highlighting its nonpathogenic status [182].…”

Rapid and Accurate Identification of Human-Associated Staphylococci by Use of Multiplex PCR

“…A total of 24 staphylococcal strains, which included 5 species with whole-genome sequences (14,23,24,32,40), were used for phylogenetic analysis of the nuc genes (Table 1). A total of 361 staphylococcal strains were studied to assess the utility of M-PCR for species identification of human-associated staphylococci, which were as follows: S. aureus (n ϭ 60), S. epidermidis (n ϭ 104), S. lugdunensis (n ϭ 26), S. haemolyticus (n ϭ 24), S. saprophyticus (n ϭ 23), S. warneri (n ϭ 23), S. hominis subsp.…”