Energy conservation by succinate decarboxylation in Veillonella parvula

Phytochemical Profile of Antibacterial Agents from Red Betel Leaf (Piper crocatum Ruiz and Pav) against Bacteria in Dental Caries

Based on data from The Global Burden of Disease Study in 2016, dental and oral health problems, especially dental caries, are a disease experienced by almost half of the world’s population (3.58 billion people). One of the main causes of dental caries is the pathogenesis of Streptococcus mutans. Prevention can be achieved by controlling S. mutans using an antibacterial agent. The most commonly used antibacterial for the treatment of dental caries is chlorhexidine. However, long-term use of chlorhexidine has been reported to cause resistance and some side effects. Therefore, the discovery of a natural antibacterial agent is an urgent need. A natural antibacterial agent that can be used are herbal medicines derived from medicinal plants. Piper crocatum Ruiz and Pav has the potential to be used as a natural antibacterial agent for treating dental and oral health problems. Several studies reported that the leaves of P. crocatum Ruiz and Pav contain secondary metabolites such as essential oils, flavonoids, alkaloids, terpenoids, tannins, and phenolic compounds that are active against S. mutans. This review summarizes some information about P. crocatum Ruiz and Pav, various isolation methods, bioactivity, S. mutans bacteria that cause dental caries, biofilm formation mechanism, antibacterial properties, and the antibacterial mechanism of secondary metabolites in P. crocatum Ruiz and Pav.

Veillonellae: Beyond Bridging Species in Oral Biofilm Ecology

The genus Veillonella comprises 16 characterized species, among which eight are commonly found in the human oral cavity. The high abundance of Veillonella species in the microbiome of both supra- and sub-gingival biofilms, and their interdependent relationship with a multitude of other bacterial species, suggest veillonellae to play an important role in oral biofilm ecology. Development of oral biofilms relies on an incremental coaggregation process between early, bridging and later bacterial colonizers, ultimately forming multispecies communities. As early colonizer and bridging species, veillonellae are critical in guiding the development of multispecies communities in the human oral microenvironment. Their ability to establish mutualistic relationships with other members of the oral microbiome has emerged as a crucial factor that may contribute to health equilibrium. Here, we review the general characteristics, taxonomy, physiology, genomic and genetics of veillonellae, as well as their bridging role in the development of oral biofilms. We further discuss the role of Veillonella spp. as potential “accessory pathogens” in the human oral cavity, capable of supporting colonization by other, more pathogenic species. The relationship between Veillonella spp. and dental caries, periodontitis, and peri-implantitis is also recapitulated in this review. We finally highlight areas of future research required to better understand the intergeneric signaling employed by veillonellae during their bridging activities and interspecies mutualism. With the recent discoveries of large species and strain-specific variation within the genus in biological and virulence characteristics, the study of Veillonella as an example of highly adaptive microorganisms that indirectly participates in dysbiosis holds great promise for broadening our understanding of polymicrobial disease pathogenesis.

Fermentative production of propionic acid: prospects and limitations of microorganisms and substrates

Propionic acid is an important organic acid with wide industrial applications, especially in the food industry. It is currently produced from petrochemicals via chemical routes. Increasing concerns about greenhouse gas emissions from fossil fuels and a growing consumer preference for bio-based products have led to interest in fermentative production of propionic acid, but it is not yet competitive with chemical production. To improve the economic feasibility and sustainability of bio-propionic acid, fermentation performance in terms of concentration, yield, and productivity must be improved and the cost of raw materials must be reduced. These goals require robust microbial producers and inexpensive renewable feedstocks, so the present review focuses on bacterial producers of propionic acid and promising sources of substrates as carbon sources. Emphasis is placed on assessing the capacity of propionibacteria and the various approaches pursued in an effort to improve their performance through metabolic engineering. A wide range of substrates employed in propionic acid fermentation is analyzed with particular interest in the prospects of inexpensive renewable feedstocks, such as cellulosic biomass and industrial residues, to produce cost-competitive bio-propionic acid. KEY POINTS: • Fermentative propionic acid production emerges as competitor to chemical synthesis. • Various bacteria synthesize propionic acid, but propionibacteria are the best producers. • Biomass substrates hold promise to reduce propionic acid fermentation cost.

Co-cultivation of Lactobacillus zeae and Veillonella cricetifor the production of propionic acid

: In this work a defined co-culture of the lactic acid bacterium Lactobacillus zeae and the propionate producer Veillonella criceti has been studied in continuous stirred tank reactor (CSTR) and in a dialysis membrane reactor. It is the first time that this reactor type is used for a defined co-culture fermentation. This reactor allows high mixing rates and working with high cell densities, making it ideal for co-culture investigations. In CSTR experiments the co-culture showed over a broad concentration range an almost linear correlation in consumption and production rates to the supply with complex nutrients. In CSTR and dialysis cultures a strong growth stimulation of L. zeae by V. criceti was shown. In dialysis cultures very high propionate production rates (0.61 g L-1h-1) with final titers up to 28 g L-1 have been realized. This reactor allows an individual, intracellular investigation of the co-culture partners by omic-technologies to provide a better understanding of microbial communities.

Complete genome sequence of Veillonella parvula type strain (Te3)

Veillonella parvula (Veillon and Zuber 1898) Prévot 1933 is the type species of the genus Veillonella in the family Veillonellaceae within the order Clostridiales. The species V. parvula is of interest because it is frequently isolated from dental plaque in the human oral cavity and can cause opportunistic infections. The species is strictly anaerobic and grows as small cocci which usually occur in pairs. Veillonellae are characterized by their unusual metabolism which is centered on the activity of the enzyme methylmalonyl-CoA decarboxylase. Strain Te3^T, the type strain of the species, was isolated from the human intestinal tract. Here we describe the features of this organism, together with the complete genome sequence, and annotation. This is the first complete genome sequence of a member of the large clostridial family Veillonellaceae, and the 2,132,142 bp long single replicon genome with its 1,859 protein-coding and 61 RNA genes is part of the Genomic Encyclopedia of Bacteria and Archaea project.

ATP synthesis by decarboxylation phosphorylation

Adenosine triphosphate (ATP) is used as a general energy source by all living cells. The free energy released by hydrolyzing its terminal phosphoric acid anhydride bond to yield ADP and phosphate is utilized to drive various energy-consuming reactions. The ubiquitous F(1)F(0) ATP synthase produces the majority of ATP by converting the energy stored in a transmembrane electrochemical gradient of H(+) or Na(+) into mechanical rotation. While the mechanism of ATP synthesis by the ATP synthase itself is universal, diverse biological reactions are used by different cells to energize the membrane. Oxidative phosphorylation in mitochondria or aerobic bacteria and photophosphorylation in plants are well-known processes. Less familiar are fermentation reactions performed by anaerobic bacteria, wherein the free energy of the decarboxylation of certain metabolites is converted into an electrochemical gradient of Na(+) ions across the membrane (decarboxylation phosphorylation). This chapter will focus on the latter mechanism, presenting an updated survey on the Na(+)-translocating decarboxylases from various organisms. In the second part, we provide a detailed description of the F(1)F(0) ATP synthases with special emphasis on the Na(+)-translocating variant of these enzymes.

The essential role of fumarate reductase in haem-dependent growth stimulation of Bacteroides fragilis

Haem is required for optimal growth of the bacterial anaerobe Bacteroides fragilis. Previous studies have shown that growth in the presence of haem is coincident with increased yields of ATP from glucose, expression of b-type cytochromes and expression of fumarate reductase activity. This paper describes the identification of the genes that encode the cytochrome, iron-sulfur cluster protein and flavoprotein of the B. fragilis fumarate reductase. These genes, frdC, frdA and frdB, respectively, are organized in an operon. Nonpolar, in-frame deletions of frdC and frdB were constructed in the B. fragilis chromosome. These mutant strains had no detectable fumarate reductase or succinate dehydrogenase activity. In addition, the frd mutant strains showed a threefold increase in generation time, relative to the wild-type strain. Growth of these mutant strains was fully restored to the wild-type rate by the introduction of a B. fragilis replicon containing the entire frd operon. Growth of the frd mutant strains was partially restored by supplementing the growth medium with succinate, indicating that the frd gene products function as a fumarate reductase. During growth on glucose, the frd mutant strains showed a threefold decrease in cell mass yield, relative to the wild-type strain. These data indicate that fumarate reductase is important for both energy metabolism and succinate biosynthesis in B. fragilis.

Energetics and kinetics of lactate fermentation to acetate and propionate via methylmalonyl-CoA or acrylyl-CoA

Fermentation balances and growth yields were determined with various bacteria fermenting lactate to acetate plus propionate either via methylmalonyl-CoA or via acrylyl-CoA. All strains fermented lactate to acetate plus propionate at approximately a 1:2 ratio. Growth yields of Propionibacterium freudenreichii were more than twice as high as those of Clostridium homopropionicum or Veillonella parvula. Hydrogen was formed as a side product to a significant extent only by V. parvula and Pelobacter propionicus; the latter formed hydrogen preferentially when using ethanol as substrate. Acrylyl-CoA reductase of C. homopropionicum and Clostridium neopropionicum was found nearly exclusively in the cytoplasm thus confirming that this reduction step is unlikely to be involved in energy conservation. C. homopropionicum exhibited higher K(S) and higher micro(max) values, as well as higher specific substrate turnover rates than P. freudenreichii. The results allow us to conclude that C. homopropionicum using the acrylyl-CoA pathway with low growth yield obtains its specific competitive advantage compared to P. freudenreichii not through higher substrate affinity or metabolic shift toward enhanced acetate-plus-hydrogen formation but through faster specific substrate turnover.

Methylmalonyl-CoA decarboxylase from Propionigenium modestum--cloning and sequencing of the structural genes and purification of the enzyme complex

Methylmalonyl-CoA decarboxylase catalyses the only energy-conserving step during succinate fermentation by Propionigenium modestum: the decarboxylation of (S)-methylmalonyl-CoA to propionyl-CoA is coupled to the vectorial transport of Na+ across the cytoplasmic membrane, thereby creating a sodium ion motive force that is used for ATP synthesis. By taking advantage of the sequence similarity between the beta-subunits of other Na+-transport decarboxylases, a portion of the P. modestum beta-subunit gene was amplified by PCR with degenerated primers. The cloned PCR product then served as homologous probe for cloning suitable fragments from genomic DNA. Sequence analysis of a 3.7-kb region identified four genes which probably form a transcriptional unit, mmdADCB. Remarkably, a mmdE gene which is present in the homologous mmdADECB cluster from Veillonella parvula and encodes the 6-kDa epsilon-subunit, is missing in P. modestum. By sequence comparisons, the following functions could be assigned to the P. modestum proteins: MmdA (56.1 kDa; alpha-subunit), carboxyltransferase; MmdB (41.2 kDa; beta-subunit), carboxybiotin-carrier-protein decarboxylase; MmdC (13.1 kDa; gamma-subunit), biotin carrier protein. MmdD (14.2 kDa; delta-subunit) presumably is essential for the assembly of the complex, as shown for the corresponding V. parvula protein. Methylmalonyl-CoA decarboxylase was solubilized from membranes of P. modestum with n-dodecylmaltoside and enriched 15-fold by affinity chromatography on monomeric avidin resin. The purified protein was composed of four subunits, three of which were identified by N-terminal sequence analysis as MmdA, MmdD, and MmdC. The purified enzyme exhibited a specific activity of up to 25 U/mg protein and an apparent Km value for (S)-methylmalonyl-CoA of approximately 12 microM. Compared to the five-subunit complex of V. parvula, the four-subunit enzyme of P. modestum appeared to be more labile, presumably a consequence of the lack of the epsilon-subunit.

Comparison of Batch Culture Growth and Fermentation of a PoultryVeillonellaIsolate and SelectedVeillonellaSpecies Grown in a Defined Medium

The objective of this study was to develop a defined medium for quantitating nutritional requirements and fermentation products of a poultry cecal isolate of Veillonella and to compare these parameters with representative Veillonella species. The poultry isolate is one of 29 organisms from a continuous-flow culture that has been shown to be effective against Salmonella colonization in broilers. When the Veillonella species were grown in anaerobic batch culture, propionate and acetate were the only volatile fatty acids detected. Lactate was needed to provide energy for the growth of the Veillonella in the defined medium. The poultry isolate had significantly (p< 0.05) higher Y(lactate)(g of dry cell weight per mole of lactate utilized) and dry cell weight than the other Veillonella species when grown on amino acid supplemented defined media. Cultures of the Veillonella species in the defined medium grown with supplemented amino acids aspartate, threonine, arginine, and serine indicated that these amino acids were metabolized to acetate and propionate. Amino acid analysis on media inoculated with either V. atypica or the poultry isolate also indicated that these organisms may have different amino acid preferences. For nearly all of the amino acid supplemented media combinations the poultry isolate utilized significantly (p< 0.05) more threonine and serine whereas V. atypica utilized significantly (p< 0.05) more aspartate. The defined medium supported growth of all of the Veillonella species tested and should enable further in-depth physiological studies to be conducted on the poultry Veillonella studies.