Complete sequencing and pan-genomic analysis of Lactobacillus delbrueckii subsp. bulgaricus reveal its genetic basis for industrial yogurt production

Lactobacillus delbrueckii subsp. bulgaricus (Lb. bulgaricus) is an important species of Lactic Acid Bacteria (LAB) used for cheese and yogurt fermentation. The genome of Lb. bulgaricus 2038, an industrial strain mainly used for yogurt production, was completely sequenced and compared against the other two ATCC collection strains of the same subspecies. Specific physiological properties of strain 2038, such as lysine biosynthesis, formate production, aspartate-related carbon-skeleton intermediate metabolism, unique EPS synthesis and efficient DNA restriction/modification systems, are all different from those of the collection strains that might benefit the industrial production of yogurt. Other common features shared by Lb. bulgaricus strains, such as efficient protocooperation with Streptococcus thermophilus and lactate production as well as well-equipped stress tolerance mechanisms may account for it being selected originally for yogurt fermentation industry. Multiple lines of evidence suggested that Lb. bulgaricus 2038 was genetically closer to the common ancestor of the subspecies than the other two sequenced collection strains, probably due to a strict industrial maintenance process for strain 2038 that might have halted its genome decay and sustained a gene network suitable for large scale yogurt production.     

Calorie restriction in overweight males ameliorates obesity-related metabolic alterations and cellular adaptations through anti-aging effects,possibly including AMPK and SIRT1 activation

Background

Calorie restriction (CR) is accepted as an experimental anti-aging paradigm. Several important signal transduction pathways including AMPK and SIRT1 are implicated in the regulation of physiological processes of CR. However, the mechanisms responsible for adaptations remain unclear in humans.

Scope of review

Four overweight male participants were enrolled and treated with 25% CR of their baseline energy requirements for 7 weeks. Characteristics, including body weight (BW), body mass index (BMI), %fat, visceral fat area (VFA), mean blood pressure (MBP) and VO₂ max, as well as metabolic parameters, such as insulin, lipid profiles and inflammatory makers and the expression of phosphorylated AMPK and SIRT1 in peripheral blood mononuclear cells (PBMNCs), were determined at baseline and then after 7 weeks. In addition, we assessed the effects of the serum collected from the participants on AMPK and SIRT1 activation and mitochondrial biogenesis in cultured human skeletal muscle cells.

Major conclusions

After CR, BW, BMI, %fat, VFA and MBP all significantly decreased, while VO₂ max increased, compared to those at baseline. The levels of fasting insulin, free fatty acid, and inflammatory makers, such as interleukin-6 and visfatin, were significantly reduced, whereas the expression of phosphorylated AMPK and SIRT1 was significantly increased in PBMNCs collected after CR, compared to those at baseline. The skeletal muscle cells that were cultured in serum collected after CR showed an increase in AMPK and SIRT1 activity as well as mitochondrial biogenesis.

General significance

CR is beneficial for obesity-related metabolic alterations and induces cellular adaptations against aging, possibly through AMPK and SIRT1 activation via circulating factors.     

Amino Acid Sequence of αkSubstance,a Mating Pheromone of Saccharomyces kluyveri

A fraction containing IgA (IgA-rich fraction) was prepared from bovine colostrum by anion exchange chromatography using DEAE-Sephadex A-50 and gel filtration on Sephadex G-200. A large amount of IgG1-dimer was found in this fraction, which could not be separated from IgA by repeated gel filtration.

The Fc fragment of bovine colostral IgG (IgG-Fc) was prepared from papain digestion mixtures. IgG-Fc was found to be heterogeneous on DEAE-cellulose column chromatography. Two IgG-Fc fractions were obtained, but no antigenic difference was found between them. Anti-IgG-Fc antibodies raised in rabbits by injection of these Fc preparations reacted only with IgG1 and IgG2. An immunoadsorbent (anti-IgG-Fc-Sepharose) was prepared by coupling these anti-IgG-Fc antibodies to CNBr-activated Sepharose 4B.

IgA was purified from the IgA-rich fraction by affinity chromatography on anti-IgG-Fc-Sepharose adsorbent. IgG1-dimer was effectively removed by this treatment. The purified sample gave only one precipitin arc characteristic of IgA on immunoelectrophoresis with multiple anti-bovine colostral whey antiserum. A small amount of IgA was found to be adsorbed to the affinity column nonspecifically.

When a rabbit was immunized with the purified IgA, besides anti-IgA antibodies, antibodies against the secretory component (SC) were found in the antiserum. This finding leads us to expect that the purified IgA is secretory IgA containing SC.     

Chemical Structure of Mating Pheromone Peptides, αsk1 and αsk3 Pheromones,Produced by Mating Type α Cells of Saccharomyces kluyveri

Three peptides, α^sk1, α^sk2 and α^sk3 pheromones, have been isolated as α-mating pheromones of Saccharomyces kluyveri, the primary structure of the main active component, α^sk2 pheromone, having already been determined. The unknown N-terminus of α^sk1 pheromone was elucidated to be 1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (β-CAR) by mass and NMR spectrometric analyses. Synthetic β-CAR-His-Trp-OH was identical with N-terminal tripeptide fragment obtained from α^sk1 pheromone, and the primary structure of α^sk1 pheromone was determined as β-CAR-His-Trp-Leu-Ser-Phe-Ser-Lys-Gly-Glu-Pro-Met(O)-Tyr-OH. The amino acid sequence of α^sk3 pheromone was determined as H-Trp-His-Trp-Leu-Ser-Phe-Ser-Lys-Gly-Glu-Pro-Met-OH by comparing the enzymatic fragments with those of α^sk2 pheromone.     

Nerve and behavioral responses of mice to various umami substances

Food contains various taste substances. Among them, umami substances play an important role with regard to the perception of the taste of food, but, few studies have examined the taste characteristics of representative umami substances other than monosodium L-glutamate (MSG). By conducting mouse behavioral studies (the 48-h 2-bottle preference test and the conditioned taste aversion test) and assessing gustatory nerve responses, we investigated the taste characteristics of unique umami substances, including sodium succinate, L-theanine, betaine, and the enantiomer of MSG, D-MSG. Furthermore, we examined the synergy of umami with inosine 5'-monophoshate (IMP). In the case of the mice, sodium succinate had an umami taste and showed strong synergy with IMP. L-theanine showed synergy with IMP but did not have an umami taste without IMP. In contrast, betaine did not have an umami taste or synergy with IMP. D-MSG might have weak synergy with IMP.     

Structures and synthesis of seed-germination inhibitors from hibiscus rosa-sinensis

8-Nonynoic, 9-decynoic acids and their methyl esters were isolated for the first time as natural products from Hibiscus rosa-sinensis. They were inhibitors of the germination of lettuce seeds and were synthesized via o-nitrophenyl selenides.     

A protein from a parasitic microorganism, Rickettsia prowazekii, can cleave the signal sequences of proteins targeting mitochondria

The obligate intracellular parasitic bacteria rickettsiae are more closely related to mitochondria than any other microbes investigated to date. A rickettsial putative peptidase (RPP) was found to resemble the alpha and beta subunits of mitochondrial processing peptidase (MPP), which cleaves the transport signal sequences of mitochondrial preproteins. RPP showed completely conserved zinc-binding and catalytic residues compared with beta-MPP but barely contained any of the glycine-rich loop region characteristic of alpha-MPP. When the biochemical activity of RPP purified from a recombinant source was analyzed, RPP specifically hydrolyzed basic peptides and presequence peptides with frequent cleavage at their MPP-processing sites. Moreover, RPP appeared to activate yeast beta-MPP so that it processed preproteins with shorter presequences. Thus, RPP behaves as a bifunctional protein that could act as a basic peptide peptidase and a somewhat regulatory protein for other protein activities in rickettsiae. These are the first biological and enzymological studies to report that a protein from a parasitic microorganism can cleave the signal sequences of proteins targeted to mitochondria.