Lactobacillus sakei is a psychrotrophic lactic acid bacterium found naturally on fresh meat and fish. This microorganism is widely used in the manufacture of fermented meats and has biotechnological potential in biopreservation and food safety. We have explored the 1,884,661-base-pair (bp) circular chromosome of strain 23K encoding 1,883 predicted genes. Genome sequencing revealed a specialized metabolic repertoire, including purine nucleoside scavenging that may contribute to an ability to successfully compete on raw meat products. Many genes appear responsible for robustness during the rigors of food processing – particularly resilience against changing redox and oxygen levels. Genes potentially responsible for biofilm formation and cellular aggregation that may assist the organism to colonize meat surfaces were also identified. This genome project is an initial step for investigating new biotechnological approaches to meat and fish processing and for exploring fundamental aspects of bacterial adaptation to these specific environments.

Lactobacillus sakei is one of the most important bacterial species involved in meat preservation and meat fermentation. In the last fifteen years, numerous studies have focused on this species due to its important role in food microbiology. The present paper reviews current knowledge of this emerging species in the fields of taxonomy, phylogeny and physiology, and metabolism. Recent developments in genetic tools and molecular genetics will also be emphasized to evaluate future prospects.

Lactobacillus sakei is one of the most important bacterial species involved in meat preservation and meat fermentation. In the last fifteen years, numerous studies have focused on this species due to its important role in food microbiology. The present paper reviews current knowledge of this emerging species in the fields of taxonomy, phylogeny and physiology, and metabolism. Recent developments in genetic tools and molecular genetics will also be emphasized to evaluate future prospects.

Lactobacillus sakei is a lactic acid bacterium commonly found on meat and meat products. Meat is a rich substrate but contains small amounts of sugars, mainly glucose and ribose. The phosphotransferase system (PTS) is a multienzymatic complex responsible for sugar uptake. It is also involved in the regulation of metabolism through various mechanisms (catabolite activation and repression, inducer expulsion and exclusion). The ptsHI operon of L. sakei, encoding the general enzymes of the PTS, was studied and mutants were constructed. On ribose, these mutants grow twice as fast as the wild-type strain. This phenotype was never described in other bacteria and suggests that the PTS regulates ribose utilization. When compared to what is known from the regulations involving the PTS in other bacteria, this mechanism might be new. In Bacillus subtilis and Escherichia coli, in which ribose catabolism was investigated, ribose is transported by an ABC transporter, encoded by rbsABCD genes and then phosphorylated by the rbsK encoded ribose kinase. Ribose-5P is then metabolized through the pentose-P pathway involving xylulose-5P phosphoketolase and acetate kinase. Whereas phosphoketolase and acetate kinase activities remained unchanged in L. sakei ptsI mutants, ribose kinase activity and uptake were increased by a factor of 2.5 and 1.5, respectively. The target of the PTS regulation would thus be transport and/or phosphorylation of ribose. The gene cluster encoding a ribose transporter, ribose kinase and a regulator was cloned and sequenced. In L. sakei no gene encoding RbsA, RbsB or RbsC could be found. However, rbsD was present as well as a new gene rbsU, encoding a protein homologous to a glucose transporter responsible for facilitated diffusion of glucose. The rbsUDK operon is induced by ribose via the regulator RbsR encoded by rbsR located downstream of rbsUDK. In ptsI mutants, this operon was not overexpressed on ribose. This shows that the regulation of ribose utilization is not a transcriptional regulation. Upstream from the rbs operon, a gene encoding acetate kinase (ackA) was found. In other bacteria in which these genes were identified, ackA and the rbs operon are not linked. Moreover, in B. subtilis, ackA is regulated by catabolite activation whereas the rbs operon is repressed by catabolite repression, two mechanisms involving the PTS. In L. sakei, ackA and the rbs operon are adjacent on the chromosome and they are not regulated as described above. We propose that in this species, ribose and glucose utilization is regulated in a different way, allowing L. sakei to catabolize both glucose and ribose, the sole sugars present in meat.

Three porcine muscles (m. longissimus dorsi, masseter and trapezius), chosen to represent the three main metabolic types, from 18 carcasses had their free amino acids and dipeptides quantified by reverse-phase high performance liquid chromatography (HPLC) in aqueous extracts derivatized with phenyl isothiocyanate. Of the 25 measured compounds, four amino acids and the dipeptide carnosine were closely related to the metabolic type of the three muscles. Masseter, a red oxidative muscle, had the highest contents of aspartic acid, glutamine and taurine. Longissimus dorsi, a white glycolytic muscle was characterised by the highest contents of β-alanine and carnosine. Trapezius, an intermediate muscle, had intermediate contents. These results show that free amino acid and dipeptide contents could partly explain differences in taste of muscles from the same species.

Pigs of similar genetic backgrounds and feeding regimes were slaughtered in two abattoirs, one carrying out dehairing by scalding and the other by singeing. One ham from each of 80 carcasses was retained. Sixteen fresh hams (8 from each dehairing technique) were used for analysis while 64 hams were processed into dry-cured ham. Sixteen hams (8 from each dehairing technique) were taken for analysis at end of salting (day 14), end of rest (day 78), mid-processing (day 127) and end of processing (day 251). During processing, the water content of all muscles decreased while the salt content increased. The salt concentration in muscle water tended to equalize in all muscles. The nitrogen content of desalted dry matter (i.e. dry muscle tissue) decreased in both Biceps femoris and Semimembranosus. The content of every free amino acid increased with time, except for taurine and glutamine. Electrophoresis of the low ionic strength-soluble fractions showed all protein bands decreased during processing. Electrophoresis of the myofibrillar fractions indicated changes in all bands except actin (42kDa). These changes were more marked in the Semimembranosus than the Biceps femoris in the earlier processing steps. Ultrastructural changes were more marked in Semimembranosus than Biceps femoris. Hardness and chewiness increased in both muscles during the first half of processing then returned to values close to the initial ones in Semimembranosus but changed little in Biceps femoris. The scalded hams lost more weight than the singed ones during processing. The salt content was higher in scalded hams. Water-soluble nitrogen and NPN were higher in singed hams at the end of processing. The scalded hams were saltier and pungent. They had more pronounced aromas of dry ham, rancidity and hazelnut, and less aroma of fresh meat. Their texture was drier and less mellow.

The 80 hams of 40 pig carcasses from one slaughter batch were taken on the day after slaughter. The 40 left hams were dry-cured. Groups of 10 hams were taken for analysis at 74 days (end of rest), 81 days (end of heating), 179 days (mid-seasoning) and 273 days (end of seasoning) after the beginning of processing. A slice of about 150 g was taken in the middle of the Biceps femoris and used for analysis of nitrogen fractions and free amino acids by HPLC. Levels of insoluble nitrogen compounds did not vary significantly, while levels of soluble protein nitrogen decreased strongly from 26 to 16% of total nitrogen, with the fastest decrease observed between days 179 and 273. Levels of non-protein nitrogen increased regularly during the processing from 12 to 23% of total nitrogen. Nitrogen of free amino acids ranged from 3·6% in fresh muscle to 16·6% of total nitrogen at day 179, then decreased to 4·4% of the total nitrogen at the end of the processing. The HPLC method allowed the identification of 29 compounds, among which 27 were amino acids and 2 were dipeptides. The average levels of free amino acids of non-protein origin tended to decrease before day 74, then to increase until day 179 and to decrease again. The levels of compounds of protein origin increased or tended to increase from the beginning until day 179, then decreased.

The left hams of 20 pig carcasses were processed by dry-curing for either 179 (n = 10) or 273 days (n = 10). The Biceps femoris was taken at the end of the processing and submitted to chemical and sensory analyses. The following chemical traits were determined: pH, moisture, salt content, fatty acid content and composition of lipid classes (triglycerides, phospholipids, free fatty acids), nitrogen fractions (soluble and insoluble protein, non-protein nitrogen, free amino acids) and volatile compounds. Sensory analysis was performed by a panel of 12 trained members, who scored texture traits (firmness, dryness, fibrousness, mellowness), taste (salty, acid), intensity of aromas (typical of dry ham, fresh meat, fat, cured meat, rancid, metal), persistence of dry ham aroma, persistence of taste after deglutition, persistence of astringency, persistence of metallic taste. The sensory qualities of dry-cured ham showed noticeable changes between days 179 and 273. Firmness, dryness and intensities of aromas typical of dry-cured ham and cured meat were enhanced with time. Neither pH, moisture nor salt content played a noticeable role in determining the sensory quality of dry-cured ham. Among the volatile compounds, the levels of several ketones and 1-butanol were significantly correlated with the aromas of dry ham and cured meat, while rancid aroma was related to aldehydes, ethylacetate, 2,3-pentanedione and nonane. Therefore, the aromas of dry ham and cured meat appeared to be determined mainly by the products of lipid oxidation. However, they were related also to unidentified volatile compounds, whose identification would be of particular interest.

The quantitative assay described in the preceding paper (Pessac et al., '77) was used to study the effects of serum and various proteins on isotypic adhesion of chick embryo neural retina cells. Fetal bovine, chicken, horse, rabbit and human sera promoted cell adhesion to the same extent. The same sera also enhanced isotypic adhesion of cells from other organs showing that the cell adhesion promoting activity of sera was not organ specific. Neural retina (NR) cell collection in serum supplemented medium was not modified by protein synthesis or metabolic inhibitors and was temperature dependent with a maximum at 38 degrees C. The higher temperature does not seem to be required for repair of the cell surface after dissociation, but for the process of adhesion itself. Various serum fractions and egg albumin showed a cell adhesion promoting activity similar to that of sera.

FEBS LettersVolume 60, Issue 2 p. 290-293 Full-length articleFree Access Intercellular adhesion of neuroretina chick embryo cells: Enhancement by bovine serum albumin and derivates Monique Cornet, Monique Cornet >Centre de Biophysique Moléculaire, C.N.R.S. 45045 Orléans Cedex FranceSearch for more papers by this authorFrançoise Alliot, Françoise Alliot Institut d'Immunobiologie, Hôpital Broussais, 96 rue Didot, 75674 Paris Cedex 14 FranceSearch for more papers by this authorBernard Pessac, Bernard Pessac Institut d'Immunobiologie, Hôpital Broussais, 96 rue Didot, 75674 Paris Cedex 14 FranceSearch for more papers by this authorMichel Monsigny, Michel Monsigny >Centre de Biophysique Moléculaire, C.N.R.S. 45045 Orléans Cedex FranceSearch for more papers by this author Monique Cornet, Monique Cornet >Centre de Biophysique Moléculaire, C.N.R.S. 45045 Orléans Cedex FranceSearch for more papers by this authorFrançoise Alliot, Françoise Alliot Institut d'Immunobiologie, Hôpital Broussais, 96 rue Didot, 75674 Paris Cedex 14 FranceSearch for more papers by this authorBernard Pessac, Bernard Pessac Institut d'Immunobiologie, Hôpital Broussais, 96 rue Didot, 75674 Paris Cedex 14 FranceSearch for more papers by this authorMichel Monsigny, Michel Monsigny >Centre de Biophysique Moléculaire, C.N.R.S. 45045 Orléans Cedex FranceSearch for more papers by this author First published: December 15, 1975 https://doi.org/10.1016/0014-5793(75)80733-2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL References 1 J. Holtfreter, Ann. N.Y. Acad. Sci., 49, (1948), 709– 760. 2 A.A. Moscona, Exptl. Cell Res., 22, (1961), 455– 475. 3 B. Pessac, F. Alliot, A. Girouard, Compt. Rend. Acad. Sci. Paris, 276, (1973), 3645– 3648. 4 Pessac, B., Alliot, F. and Girard, A., submitted to J. Cell Physiol. 5 Pessac, B., Alliot, F., Girard, A. and Cornet, M. submitted to J. Cell. Physiol. 6 B.J. Davis, Ann. N.Y. Acad. Sci., 121, (1964), 404– 427. 7 P. Grabar, C.A. Williams, Biochim. Biophys. Acta, 10, (1953), 193– 194. 8 R. Fields, Met. Enzymol., 25, (1972), 464– 468. 9 R.F. Chen, J. Biol. Chem., 242, (1967), 173– 181. 10 D.S. Goodman, Science, 125, (1957), 1296– 1297. 11 J.F. Riordan, B.L. Vallee, Met. Enzymol., 25, (1972), 494– 499. 12 J.F. Riordan, B.L. Vallee, Met. Enzymol., 25, (1972), 500– 506. 13 A.F.S.A. Habeeb, H.G. Cassidy, S.J. Singer, Biochim. Biophys. Acta, 29, (1958), 587– 593. 14 H.R. Horton, D.E. Koshland, J. Am. Chem. Soc., 87, (1965), 1126– 1132. 15 J.J. Deman, E.A. Bruyneel, Exptl. Cell. Res., 89, (1974), 206– 216. 16 B. Pessac, V. Defendi, Science, 175, (1972), 898– 900. 17 C.W. Orr, S. Roseman, J. Membrane Biol., 1, (1969), 125– 143. 18 S.J. Kleinschuster, A.A. Moscona, Exptl. Cell. Res., 70, (1972), 397– 410. 19 S. Nordling, A. Vaheri, E. Saxén, K. Penttinen, Exptl. Cell. Res., 37, (1965), 406– 419. Volume60, Issue2December 15, 1975Pages 290-293 ReferencesRelatedInformation