RESUMO
Phospholipid-protein interactions play important roles in regulating the function and morphology of photosynthetic membranes in purple phototrophic bacteria. Here, we characterize the phospholipid composition of intracytoplasmic membrane (ICM) from Rhodobacter (Rba.) sphaeroides that has been genetically altered to selectively express light-harvesting (LH) complexes. In the mutant strain (DP2) that lacks a peripheral light-harvesting (LH2) complex, the phospholipid composition was significantly different from that of the wild-type strain; strain DP2 showed a marked decrease in phosphatidylglycerol (PG) and large increases in cardiolipin (CL) and phosphatidylcholine (PC) indicating preferential interactions between the complexes and specific phospholipids. Substitution of the core light-harvesting (LH1) complex of Rba. sphaeroides strain DP2 with that from the purple sulfur bacterium Thermochromatium tepidum further altered the phospholipid composition, with substantial increases in PG and PE and decreases in CL and PC, indicating that the phospholipids incorporated into the ICM depend on the nature of the LH1 complex expressed. Purified LH1-reaction center core complexes (LH1-RC) from the selectively expressing strains also contained different phospholipid compositions than did core complexes from their corresponding wild-type strains, suggesting different patterns of phospholipid association between the selectively expressed LH1-RC complexes and those purified from native strains. Effects of carotenoids on the phospholipid composition were also investigated using carotenoid-suppressed cells and carotenoid-deficient species. The findings are discussed in relation to ICM morphology and specific LH complex-phospholipid interactions.
Assuntos
Proteobactérias , Rhodobacter sphaeroides , Proteobactérias/metabolismo , Fosfolipídeos/metabolismo , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/metabolismo , Rhodobacter sphaeroides/genética , Rhodobacter sphaeroides/metabolismo , Cardiolipinas/metabolismo , Carotenoides/metabolismoRESUMO
The core light-harvesting complexes (LH1) in bacteriochlorophyll (BChl) b-containing purple phototrophic bacteria are characterized by a near-infrared absorption maximum around 1010 nm. The determinative cause for this ultra-redshift remains unclear. Here, we present results of circular dichroism (CD) and resonance Raman measurements on the purified LH1 complexes in a reaction center-associated form from a mesophilic and a thermophilic Blastochloris species. Both the LH1 complexes displayed purely positive CD signals for their Qy transitions, in contrast to those of BChl a-containing LH1 complexes. This may reflect differences in the conjugation system of the bacteriochlorin between BChl b and BChl a and/or the differences in the pigment organization between the BChl b- and BChl a-containing LH1 complexes. Resonance Raman spectroscopy revealed remarkably large redshifts of the Raman bands for the BChl b C3-acetyl group, indicating unusually strong hydrogen bonds formed with LH1 polypeptides, results that were verified by a published structure. A linear correlation was found between the redshift of the Raman band for the BChl C3-acetyl group and the change in LH1-Qy transition for all native BChl a- and BChl b-containing LH1 complexes examined. The strong hydrogen bonding and π-π interactions between BChl b and nearby aromatic residues in the LH1 polypeptides, along with the CD results, provide crucial insights into the spectral and structural origins for the ultra-redshift of the long-wavelength absorption maximum of BChl b-containing phototrophs.
Assuntos
Bactérias/química , Fenômenos Fisiológicos Bacterianos , Bacterioclorofilas/análise , Bacterioclorofilas/química , Dicroísmo Circular/métodos , Complexos de Proteínas Captadores de Luz/análise , Complexos de Proteínas Captadores de Luz/química , Análise Espectral Raman/métodosRESUMO
In contrast to plants, algae and cyanobacteria that contain glycolipids as the major lipid components in their photosynthetic membranes, phospholipids are the dominant lipids in the membranes of anoxygenic purple phototrophic bacteria. Although the phospholipid compositions in whole cells or membranes are known for a limited number of the purple bacteria, little is known about the phospholipids associated with individual photosynthetic complexes. In this study, we investigated the phospholipid distributions in both membranes and the light-harvesting 1-reaction center (LH1-RC) complexes purified from several purple sulfur and nonsulfur bacteria. 31P NMR was used for determining the phospholipid compositions and inductively coupled plasma atomic emission spectroscopy was used for measuring the total phosphorous contents. Combining these two techniques, we could determine the numbers of specific phospholipids in the purified LH1-RC complexes. A total of approximate 20-30 phospholipids per LH1-RC were detected as the tightly bound lipids in all species. The results revealed that while cardiolipin (CL) exists as a minor component in the membranes, it became the most abundant phospholipid in the purified core complexes and the sum of CL and phosphatidylglycerol accounted for more than two thirds of the total phospholipids for most species. Preferential association of these anionic phospholipids with the LH1-RC is discussed in the context of the recent high-resolution structure of this complex from Thermochromatium (Tch.) tepidum. The detergent lauryldimethylamine N-oxide was demonstrated to selectively remove phosphatidylethanolamine from the membrane of Tch. tepidum.
Assuntos
Membrana Celular/metabolismo , Chromatiaceae/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Fosfolipídeos/metabolismo , Cromatóforos Bacterianos/química , Cromatóforos Bacterianos/metabolismo , Membrana Celular/química , Chromatiaceae/química , Escherichia coli/química , Escherichia coli/metabolismo , Hyphomicrobiaceae/química , Hyphomicrobiaceae/metabolismo , Complexos de Proteínas Captadores de Luz/química , Ressonância Magnética Nuclear Biomolecular , Fosfolipídeos/química , Rhodobacter sphaeroides/química , Rhodobacter sphaeroides/metabolismo , Rhodospirillum rubrum/química , Rhodospirillum rubrum/metabolismo , Espectrofotometria AtômicaRESUMO
Phylogenetic analysis indicates that microbial arsenic metabolism is ancient and probably extends back to the primordial Earth. In microbial biofilms growing on the rock surfaces of anoxic brine pools fed by hot springs containing arsenite and sulfide at high concentrations, we discovered light-dependent oxidation of arsenite [As(III)] to arsenate [As(V)] occurring under anoxic conditions. The communities were composed primarily of Ectothiorhodospira-like purple bacteria or Oscillatoria-like cyanobacteria. A pure culture of a photosynthetic bacterium grew as a photoautotroph when As(III) was used as the sole photosynthetic electron donor. The strain contained genes encoding a putative As(V) reductase but no detectable homologs of the As(III) oxidase genes of aerobic chemolithotrophs, suggesting a reverse functionality for the reductase. Production of As(V) by anoxygenic photosynthesis probably opened niches for primordial Earth's first As(V)-respiring prokaryotes.
Assuntos
Arseniatos/metabolismo , Arsenitos/metabolismo , Biofilmes/crescimento & desenvolvimento , Cianobactérias/metabolismo , Ectothiorhodospira/metabolismo , Fontes Termais/microbiologia , Fotossíntese , Anaerobiose , Arseniato Redutases/genética , Arseniato Redutases/metabolismo , Processos Autotróficos , California , Cianobactérias/crescimento & desenvolvimento , Cianobactérias/isolamento & purificação , Ectothiorhodospira/classificação , Ectothiorhodospira/crescimento & desenvolvimento , Ectothiorhodospira/isolamento & purificação , Luz , Dados de Sequência Molecular , Oxirredução , Sulfetos/metabolismoRESUMO
AIMS: To isolate and characterize bacteria from nature capable of producing poly-beta-hydroxyalkanoates in high yields from soy molasses oligosaccharides. METHODS AND RESULTS: Several strains of bacteria were obtained from enrichment cultures employing raffinose as major carbon source and inoculated with soybean field soil, lake sediment, or lake water. Many of the isolates were Bacillus species and produced polyhydroxyalkanoates (PHAs) to high yield. The raffinose-degrading isolates produced endospores, were highly saccharolytic, and both respired and fermented a variety of mono-, di-, tri- and tetrasaccharides. Strain CL1 produced 90% of cell dry mass as PHA from various sugars, including raffinose, and did so without requiring a nutrient limitation. CONCLUSIONS: Strain CL1 could be the catalyst for an industrial fermentation converting soy molasses and other waste carbohydrates to PHAs. The properties of this organism that make it ideally suited for such a fermentation include (i) its ability to use a wide variety of plant-associated carbohydrates as PHA feedstocks; (ii) its rapid growth; (iii) its ability to grow under anoxic conditions; and (iv) its ability to produce spores. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report of bacteria capable of making biodegradable plastics to high yield from soy molasses oligosaccharides.
Assuntos
Bacillus/metabolismo , Biopolímeros/metabolismo , Glycine max/metabolismo , Melaço/microbiologia , Oligossacarídeos/metabolismo , Bacillus/crescimento & desenvolvimento , Biopolímeros/química , Metabolismo dos Carboidratos , Fermentação , Hidroxibutiratos/química , Hidroxibutiratos/metabolismo , Poliésteres/química , Poliésteres/metabolismo , Rafinose/metabolismoRESUMO
Filamentous bacteria containing bacteriochlorophylls c and a were enriched from hypersaline microbial mats. Based on phylogenetic analyses of 16S rRNA gene sequences, these organisms form a previously undescribed lineage distantly related to Chloroflexus spp. We developed and tested a set of PCR primers for the specific amplification of 16S rRNA genes from filamentous phototrophic bacteria within the kingdom of "green nonsulfur bacteria." PCR products recovered from microbial mats in a saltern in Guerrero Negro, Mexico, were subjected to cloning or denaturing gradient gel electrophoresis and then sequenced. We found evidence of a high diversity of bacteria related to Chloroflexus which exhibit different distributions along a gradient of salinity from 5.5 to 16%.
Assuntos
Chlorobi/classificação , Chlorobi/genética , Ecossistema , Cloreto de Sódio , Microbiologia da Água , Chlorobi/crescimento & desenvolvimento , Meios de Cultura , Primers do DNA , Genes de RNAr , Dados de Sequência Molecular , Filogenia , RNA Ribossômico 16S/genética , Análise de Sequência de DNARESUMO
The purple nonsulfur bacterium Rhodobacter capsulatus strain B10 grew phototrophically on the aromatic compound hippurate (N-benzoyl-L-glycine) and related benzoyl amino acids. Absorption spectra, extraction, and GC/MS analysis of culture supernatants showed that hippurate was stoichiometrically converted to benzoate and glycine, with the latter used as a carbon or nitrogen source for growth. This conclusion was supported by detection of the enzyme hippuricase in permeabilized intact cells. Chemotrophic growth on hippurate by Rba. capsulatus, either at full or reduced oxygen tensions, was not observed. The type strain of Rhodobacter sphaeroides as well as four strains of Rhodopseudomonas palustris also grew phototrophically on hippurate, while several other aromatic-degrading species of purple bacteria did not.
Assuntos
Hipuratos/metabolismo , Rhodobacter capsulatus/crescimento & desenvolvimento , Rhodobacter capsulatus/metabolismo , Benzoatos/metabolismo , Cromatografia Gasosa-Espectrometria de Massas , Glicina/metabolismo , Hipuratos/química , Rhodobacter capsulatus/classificaçãoRESUMO
Primer sets were designed to target specific 16S ribosomal DNA (rDNA) sequences of photosynthetic bacteria, including the green sulfur bacteria, the green nonsulfur bacteria, and the members of the Heliobacteriaceae (a gram-positive phylum). Due to the phylogenetic diversity of purple sulfur and purple nonsulfur phototrophs, the 16S rDNA gene was not an appropriate target for phylogenetic rDNA primers. Thus, a primer set was designed that targets the pufM gene, encoding the M subunit of the photosynthetic reaction center, which is universally distributed among purple phototrophic bacteria. The pufM primer set amplified DNAs not only from purple sulfur and purple nonsulfur phototrophs but also from Chloroflexus species, which also produce a reaction center like that of the purple bacteria. Although the purple bacterial reaction center structurally resembles green plant photosystem II, the pufM primers did not amplify cyanobacterial DNA, further indicating their specificity for purple anoxyphototrophs. This combination of phylogenetic- and photosynthesis-specific primers covers all groups of known anoxygenic phototrophs and as such shows promise as a molecular tool for the rapid assessment of natural samples in ecological studies of these organisms.
Assuntos
Bactérias/genética , Bactérias/isolamento & purificação , Proteínas de Bactérias , Primers do DNA , Eletroforese em Gel de Poliacrilamida/métodos , Fotossíntese , Filogenia , Anaerobiose , Chlorobi/genética , Chlorobi/isolamento & purificação , DNA Bacteriano/genética , DNA Ribossômico/genética , Genes de RNAr , Complexo de Proteínas do Centro de Reação Fotossintética/genética , Reação em Cadeia da Polimerase , RNA Ribossômico 16S/genéticaRESUMO
Although enrichment cultures for anoxygenic phototrophic heliobacteria commonly contain sporulating cells, once strains of heliobacteria are obtained in pure culture, they all but cease to sporulate. In fact, some species of heliobacteria have never been observed to sporulate. Thus, despite their phylogenetic connection to endospore-forming bacteria, the question of sporulation capacity in heliobacteria remains open. We have investigated this problem using PCR and Southern hybridization as tools and show here that all recognized species of heliobacteria tested, as well as several unclassified strains, contain homologs to the ssp genes of Clostridium and Bacillus species, genes that encode key sporulation-specific proteins. It can therefore be concluded that as a group, heliobacteria are likely all to be endospore-forming bacteria in agreement with their phylogenetic placement within the 'low GC' Gram-positive bacteria.
Assuntos
Proteínas de Bactérias/genética , Clostridium perfringens/genética , DNA Bacteriano/genética , Proteínas de Escherichia coli , Esporos Bacterianos/genética , Proteínas de Bactérias/análise , Southern Blotting , DNA Bacteriano/análise , Reação em Cadeia da Polimerase , Esporos Bacterianos/fisiologiaRESUMO
Carotenoids extracted from cells of a novel alkaliphilic purple nonsulfur bacterium Rhodobaca bogoriensis strain LBB1 included unusual carotenoids in the spheroidene pathway; demethylspheroidene, demethylspheroidenone, neurosporene and spheroidenone. Spheroidene was present in only small amounts, and the demethyl-carotenoids demethylspheroidene and demethylspheroidenone predominated in phototrophic cultures. Furthermore, the keto-carotenoids spheroidenone and demethylspheroidenone constituted nearly half of the total carotenoids, even in strict anaerobic phototrophic cultures. Spheroidenone was, however, the sole carotenoid in aerobic cultures. Phototrophic cultures of Rbc. bogoriensis were yellow in colour and quite distinct from the brown-red colour of cultures of Rhodobacter species. The carotenogenesis pathways of Rhodobaca and Rhodobacter species are compared with special reference to two key enzymes of the spheroidene pathway, CrtA and CrtF, whose activities are thought to be responsible for the unusual carotenoid composition of Rhodobaca. This bacterium also contained bacteriochlorophyll a (p) and ubiquinone-10.
RESUMO
From enrichment cultures established for purple nonsulfur bacteria using water and sediment samples from Lake Bogoria and Crater Lake, two soda lakes in the African Rift Valley, three strains of purple nonsulfur bacteria were isolated; strain LBB1 was studied in detail. Cells of strain LBB1 were motile and spherical to rod-shaped, suggesting a relationship to Rhodobacter or Rhodovulum species, and the organism was capable of both phototrophic and chemotrophic growth on a wide variety of organic compounds. Phototrophically grown cultures were yellow to yellow-brown in color and grew optimally at pH 9 (pH range 7.5-10) and 1% NaCl (range 0-10%). In physiological studies of strain LBB1, neither photoautotrophy (H2- or sulfide-dependent) nor nitrogen fixation was observed. Absorption spectra revealed that all three strains contained bacteriochlorophyll a and carotenoids of the spheroidene pathway and synthesized only a light-harvesting (LH) I-type photosynthetic antenna complex. Electron microscopy of cells of strain LBB1 revealed a vesicular intracytoplasmic membrane system, although only a few vesicles were observed per cell. The G+C content of strain LBB1 DNA was 59 mol%, significantly lower than that of known Rhodobacter and Rhodovulum species, and its phylogeny as determined by ribosomal RNA gene sequencing placed it within the Rhodobacter/Rhodovulum clade yet distinct from all described species of either of these genera. The unique assemblage of properties observed in strain LBB1 warrants its inclusion in a new genus of purple nonsulfur bacteria and the name Rhodobaca bogoriensis is proposed herein, the genus name reflecting morphological characteristics and the species epithet referring to the habitat.
Assuntos
Rhodobacter/classificação , África , Carbono/metabolismo , Água Doce/microbiologia , Genes Bacterianos , Concentração de Íons de Hidrogênio , Microscopia Eletrônica , Dados de Sequência Molecular , Nitrogênio/metabolismo , Fotossíntese , Filogenia , Pigmentos Biológicos/metabolismo , RNA Bacteriano/genética , RNA Ribossômico 16S/genética , Rhodobacter/genética , Rhodobacter/fisiologia , Cloreto de Sódio , TemperaturaRESUMO
A new species of purple nonsulfur bacteria isolated from an Antarctic microbial mat is described. The organism, designated strain ANT.BR, was mildly psychrophilic, growing optimally at 15-18 degrees C with a growth temperature range of 0-25 degrees C. Cells of strain ANT.BR were highly motile curved rods and spirals, contained bacteriochlorophyll a, and showed a multicomponent in vivo absorption spectrum. A specific phylogenetic relationship was observed between strain ANT.BR and the purple bacterium Rhodoferax fermentans FR2T, and the two organisms shared several physiological and other phenotypic properties, with the notable exception of growth temperature optimum. Tests of genomic DNA hybridization, however, showed Rfx. fermentans FR2T and strain ANT.BR to be genetically distinct bacteria. Because of its unique set of properties, especially its requirement for low growth temperatures, we propose to recognize strain ANT.BR as a new species of the genus Rhodoferax, Rhodoferax antarcticus, named for its known habitat, the Antarctic.
Assuntos
Bactérias/classificação , Bactérias/isolamento & purificação , Betaproteobacteria/classificação , Microbiologia da Água , Regiões Antárticas , Bactérias/citologia , Fenômenos Fisiológicos Bacterianos , Bacterioclorofilas/metabolismo , Composição de Bases , Betaproteobacteria/citologia , Betaproteobacteria/isolamento & purificação , Betaproteobacteria/fisiologia , Carbono/metabolismo , Carotenoides/metabolismo , Meios de Cultura , DNA Bacteriano/química , DNA Bacteriano/genética , Genes de RNAr , Dados de Sequência Molecular , Nitrogênio/metabolismo , Filogenia , RNA Ribossômico/genética , Análise de Sequência de DNA , TemperaturaRESUMO
Growth experiments were performed with the purple nonsulfur bacterium Rhodobacter capsulatus to test its ability to use aliphatic, methyl-substituted, and unsaturated alcohols, as well as di-alcohols, as carbon sources for growth. Both phototrophic and chemotrophic growth was observed on a wide variety of such alcohols. By contrast, secondary or tertiary alcohols, or primary alcohols containing an ethyl or propyl substituent, did not support growth. In addition, preculture history and serial subculturing were found to be important factors for obtaining reliable growth of R. capsulatus on alcohols. Collectively, these results suggest that the carbon nutritional diversity of Rhodobacter capsulatus is even greater than previously suspected and that besides metabolizing organic acids and fatty acids in nature, this species may also be a major consumer of alcohols.
Assuntos
Álcoois/metabolismo , Glicóis/metabolismo , Rhodobacter capsulatus/crescimento & desenvolvimento , Meios de Cultura , Etanol/metabolismo , Luz , Rhodobacter capsulatus/metabolismoRESUMO
The microbiology of extremely hot or saline habitats is a fast moving field with many new successes in the enrichment and isolation of new organisms and in an understanding of molecular factors that impart stability on thermostable and halophilic biomolecules. The results of these studies have shed new light on our understanding of prokaryotic diversity and structural biochemistry.
Assuntos
Archaea/genética , Bactérias/genética , Adaptação Fisiológica , Archaea/crescimento & desenvolvimento , Bactérias/crescimento & desenvolvimento , DNA Arqueal/química , DNA Bacteriano/química , Conformação de Ácido NucleicoRESUMO
The complete carotenoid composition of the thermophilic green sulfur bacterium Chlorobium tepidum strain TNO was determined by spectroscopic methods. Major carotenoids were four kinds of carotenes: gamma-carotene, chlorobactene, and their 1',2'-dihydro derivatives (1',2'-dihydro-gamma-carotene and 1',2'-dihydrochlorobactene). In lesser amounts, hydroxyl gamma-carotene, hydroxyl chlorobactene, and their glucoside fatty acid esters were found. The only esterified fatty acid present was laurate, and OH-chlorobactene glucoside laurate is a novel carotenoid. In other strains of C. tepidum, the same carotenoids were found, but the composition varied from strain to strain. The overall pigment composition in cells of strain TNO was 4 mol carotenoids and 40 mol bacteriochlorophyll c per mol bacteriochlorophyll a. The effects of nicotine on carotenoid biosynthesis in C. tepidum differed from those in the thermophilic green nonsulfur bacterium Chloroflexus aurantiacus.
Assuntos
Carotenoides/isolamento & purificação , Chlorobi/química , Carotenoides/metabolismo , Chlorobi/efeitos dos fármacos , Chlorobi/metabolismo , Cromatografia Líquida de Alta Pressão , Meios de Cultura/metabolismo , Ácidos Graxos/análise , Ácidos Graxos/isolamento & purificação , Lauratos/isolamento & purificação , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Nicotina/farmacologiaRESUMO
The carotenoids of five species of heliobacteria (Heliobacillus mobilis, Heliophilum fasciatum, Heliobacterium chlorum, Heliobacterium modesticaldum, and Heliobacterium gestii) were examined by spectroscopic methods, and the C30 carotene 4,4'-diaponeurosporene was found to be the dominant pigment; heliobacteria were previously thought to contain the C40 carotenoid neurosporene. In addition, trace amounts of the C30 diapocarotenes diapolycopene, diapo-zeta-carotene, diapophytofluene, and diapophytoene were also found. Up to now, diapocarotenes have been found in only three species of chemoorganotrophic bacteria, but not in phototropic organisms. Furthermore, the esterifying alcohol of bacteriochlorophyll g from all known species of heliobacteria was determined to be farnesol (C15) instead of the usual phytol (C20). Heliobacteria may be unable to produce geranylgeranyol (C20).
Assuntos
Carotenoides/análise , Carotenoides/isolamento & purificação , Bactérias Gram-Positivas/química , Bactérias/química , Bacterioclorofilas/análise , Bacterioclorofilas/isolamento & purificação , Carotenoides/química , Farneseno Álcool/isolamento & purificação , Bactérias Gram-Positivas/metabolismo , Estrutura Molecular , Fitol/isolamento & purificaçãoRESUMO
The photosynthetic bacterium Rhodobacter capsulatus can grow with short- to long-chain fatty acids as the sole carbon source (R. G. Kranz, K. K. Gabbert, T. A. Locke, and M. T. Madigan, Appl. Environ. Microbiol. 63:3003-3009, 1997). Concomitant with growth on fatty acids is the production to high levels of the polyester storage compounds called polyhydroxyalkanoates (PHAs). Here, we describe colony screening and selection systems to analyze the production of PHAs in R. capsulatus. A screen with Nile red dissolved in acetone distinguishes between PHA producers and nonproducers. Unlike the wild type, an R. capsulatus PhaC- strain with the gene encoding PHA synthase deleted is unable to grow on solid media containing high concentrations of certain fatty acids. It is proposed that this deficiency is due to the inability of the PhaC- strain to detoxify the surrounding medium by consumption of fatty acids and their incorporation into PHAs. This fatty acid toxicity phenotype is used in selection for the cloning and characterization of heterologous phaC genes.
Assuntos
Ácidos Graxos/metabolismo , Poliésteres/metabolismo , Rhodobacter capsulatus/metabolismo , Acetona/metabolismo , Aciltransferases/genética , Clonagem Molecular , Meios de Cultura/metabolismo , Rhodobacter capsulatus/genética , Deleção de SequênciaRESUMO
Like many other prokaryotes, the photosynthetic bacterium Rhodobacter capsulatus produces high levels of polyhydroxyalkanoates (PHAs) when a suitable carbon source is available. The three genes that are traditionally considered to be necessary in the PHA biosynthetic pathway, phaA (beta-ketothiolase), phaB (acetoacetylcoenzyme A reductase), and phaC (PHA synthase), were cloned from Rhodobacter capsulatus. In R. capsulatus, the phaAB genes are not linked to the phaC gene. Translational beta-galactosidase fusions to phaA and phaC were constructed and recombined into the chromosome. Both phaC and phaA were constitutively expressed regardless of whether PHA production was induced, suggesting that control is posttranslational at the enzymatic level. Consistent with this conclusion, it was shown that the R. capsulatus transcriptional nitrogen-sensing circuits were not involved in PHA synthesis. The doubling times of R. capsulatus transcriptional nitrogen-sensing circuits were not involved in PHA synthesis. The doubling times of R. capsulatus grown on numerous carbon sources were determined, indicating that this bacterium grows on C2 to C12 fatty acids. Grown on acetone, caproate, or heptanoate, wild-type R. capsulatus produced high levels of PHAs. Although a phaC deletion strain was unable to synthesize PHAs on any carbon source, phaA and phaAB deletion strains were able to produce PHAs, indicating that alternative routes for the synthesis of substrates for the synthase are present. The nutritional versatility and bioenergetic versatility of R. capsulatus, coupled with its ability to produce large amounts of PHAs and its genetic tractability, make it an attractive model for the study of PHA production.
Assuntos
Regulação Bacteriana da Expressão Gênica , Poliésteres/metabolismo , Rhodobacter capsulatus/genética , Rhodobacter capsulatus/metabolismo , Acetona/metabolismo , Acetil-CoA C-Aciltransferase/genética , Aciltransferases/genética , Aciltransferases/metabolismo , Oxirredutases do Álcool/genética , Caproatos/metabolismo , Mapeamento Cromossômico , Cromossomos Bacterianos , Clonagem Molecular , Meios de Cultura/metabolismo , Ácidos Graxos/metabolismo , Regulação Enzimológica da Expressão Gênica , Heptanoatos/metabolismo , Plasmídeos , Biossíntese de Proteínas , Rhodobacter capsulatus/ultraestrutura , Deleção de Sequência , Transcrição GênicaRESUMO
NASA: The authors examine the presence of bacteria in extreme climates and their role in biotechnology. Within the past 30 years, scientists have discovered bacteria in areas long thought to be sterile due to extremes in heat, cold, or pH. Enzymes from these bacteria are used in many areas of industry. Examples discussed include the use of enzymes from thermophilic bacteria for polymerase chain reactions, use of enzymes in detergents, and the use of halophiles to enhance extraction of crude oil. Methods of harvesting extremozymes are discussed.^ieng
Assuntos
Archaea/fisiologia , Fenômenos Fisiológicos Bacterianos , Biotecnologia , Microbiologia Ambiental , Microbiologia Industrial , Archaea/classificação , Archaea/enzimologia , Bactérias/classificação , Bactérias/enzimologia , Evolução Biológica , Clima Frio , DNA Recombinante , Temperatura Alta , Concentração de Íons de Hidrogênio , Reação em Cadeia da Polimerase , Cloreto de Sódio , Transformação GenéticaRESUMO
Two new taxa of phototrophic heliobacteria are described: Heliobacterium gestii sp. nov. and Heliophilum fasciatum gen. nov. sp. nov. Both organisms were isolated from dry paddy soils. Cells of H. gestii were motile spirilla; cells of H. fasciatum formed cell bundles that were motile as units. Both organisms produced endospores; H. gestii endospores contained dipicolinic acid and elevated levels of calcium. As with other heliobacteria, bacteriochlorophyll g was produced in both organisms and no intracytoplasmic photosynthetic membranes were observed. Growth of H. gestii and H. fasciatum occurred under both photoheterotrophic and chemotrophic conditions; nitrogen fixation also occurred in both organisms. H. gestii and H. fasciatium showed a phylogenetic relationship to the "low GC" line of gram-positive Bacteria, but H. fasciatum was distinct from H. gestii and all other heliobacteria. The ability of H. gestii and H. fasciatum to form endospores might be a significant ecological advantage for survival in their rice soil habitat.