- Volume 140, Issue 2, 1994
Volume 140, Issue 2, 1994
- Review Article
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- Sgm Special Lecture
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- Microbiology Comment
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- Biochemistry
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Properties of a Paracoccus denitrificans mutant deleted in cytochrome c550 indicate that a copper protein can substitute for this cytochrome in electron transport to nitrite, nitric oxide and nitrous oxide
More LessSummary: Disruption of the gene for the periplasmic cytochrome c550 in Paracoccus denitrificans did not result in substantial alteration of rates of electron flow from physiological substrates to the reductases for nitrite, nitric oxide and nitrous oxide, thus confirming and extending earlier findings. In wild-type cells the chelating agent diethyldithiocarbamate (DDC) caused a partial inhibition of these electron transport processes. When the same concentrations of this inhibitor were added to a mutant of P. denitrificans in which the gene for cytochrome c550 was specifically disrupted an almost complete inhibition of these reactions was observed. It is known from previous work with the closely related organism Thiosphaera pantotropha that DDC effectively and rapidly removes copper from the periplasmic pseudoazurin that is also found in P. denitrificans. Therefore, it is concluded that in the absence of cytochrome c550, a copper protein, probably pseudoazurin, acts as the electron carrier between the cytochrome bc 1 complex and the reductases for nitrite, nitric oxide and nitrous oxide. Cells with the gene for cytochrome c550 deleted continued to give a positive Nadi test.
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Multiple high activity cysteine proteases of Leishmania mexicana are encoded by the Imcpb gene array
More LessSummary: The interrelationship of the multiple cysteine proteases (CPs) found characteristically at high activity in Leishmania mexicana amastigotes has been investigated. The mature forms of the five enzymes of groups B and C, which have subtly different substrate preferences, are the same size. Enzymically deglycosylated group A CP proteins also have the same molecular mass. Proteases of all three groups are specifically recognized by antisera raised against the group B or group C CPs. In addition, CPs of groups A, B and C have highly similar N-terminal amino acid sequences. The consensus sequence matches that predicted from the sequenced Imcpb gene, which occurs in a tandem array of over ten similar genes. Thus, the results are consistent with the groups A, B and C CPs being products of different Imcpb genes within the array, the different genes encoding CPs with identical N-termini, but with limited amino acid substitutions within the mature enzyme accounting for the different properties of the CPs. Evidence is also presented to indicate membrane-association of proteolytically active but less processed forms of Imcpb products.
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The linear-plasmid-encoded toxin produced the yeast Pichia acaciae: characterization an comparison with the toxin of Kluyveromyce: lactis
More LessSummary: The toxin produced by Pichia acaciae was purified and its properties comp to those of the toxin from Kluyveromyces lactis. Like this toxin, the P. aca toxin is a protein comprised of three subunits (molecular masses 110, 39 a 38 kDa) with an associated chitinase activity and a pH optimum between 7.0 and 7.5. P. acaciae toxin also caused G1 cell cycle arrest. Of the thirteen recessive alleles that provided resistance in Saccharomyces cerevisiae to A lactis toxin, only three also conferred resistance to P. acaciae toxin. Simila and differences in the interactions of the two toxins with yeast cells are discussed.
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- Development And Structure
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Modulation of Pasteurella multocida capsular polysaccharide during growth under ironrestricted conditions and in vivo
More LessSummary: Addition of the iron chelators 2,2-dipyridyl, deferoxamine mesylate or apotransferrin to culture media affected the composition and the morphology of Pasteurella multocida cells. Cells grown under iron-restricted conditions expressed iron-regulated proteins and, in addition, iron deprivation markedly reduced the amount of capsular material covering the cells of P. multocida. The addition of iron neutralized the effect of these chelators on capsule production. Cells of P. multocida grown under iron-restricted conditions were more labelled by gold particles coated with polymyxin which is known to interact with the lipid A-core region of lipopolysaccharides, and showed increased affinity for porcine respiratory tract mucus than cells grown under iron-sufficient conditions. Bacterial cells grown in vivo in peritoneal chambers in rats were also only covered by a thin layer (15-20 nm) of capsular material. Although the capsule is believed to be an important virulence factor, our data indicate that under iron-restricted conditions, such as those encountered in vivo, P. multocida may not be heavily encapsulated.
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The role of the cytoskeleton in the polarized growth of the germ tube in Candida albicans
More LessSummary: Cells of the dimorphic yeast Candida albicans are easily induced to germinate in synchrony. Using germinating cells of strain FC18, we examined the effects of several drugs that are known to affect the cytoskeleton on growth and cytoskeletal organization. Cytochalasin A (CA), an inhibitor of actin function, inhibited the germination of the yeast cells and changed the cylindrical expansion of the apex of the germ tube to swelling growth. Effects of CA on the organization of actin were examined with rhodamine-phalloidin (Rh-Ph), which specifically stains F-actin. In CA-untreated cells, Rh-Ph staining resulted in condensed dot-like fluorescence at the growing tip, as well as filamentous fluorescence (actin cables) that ran from the apex to the basal region. In CA-treated cells, condensed dot-like fluorescence was still observed at the swelling tip, but actin cables had disappeared completely. This result indicates that CA does not affect the asymmetrical distribution of actin, and suggests that the actin cables are not required for maintenance of the polarized localization of actin. Benomyl, an anti-microtubule drug, inhibited the germination of yeast cells and the apical growth of germinated cells. Benomyl not only disrupted microtubules (MTs), but also affected the distribution of actin. In benomyl-treated cells, actin dots were randomly dispersed all over the cell. This result indicates that benomyl destroyed the mechanism that maintains the asymmetrical distribution of actin, and suggests that MTs are involved in such a mechanism. The polarized localization of organelles is one of the most important factors associated with dimorphism. Our data suggest that the cytoskeleton, composed of actin and MTs, is involved in the control of polarity in the hyphal growth of C. albicans, and that actin and MTs are interrelated in the establishment of polarity.
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The role of microfilaments and microtubules during pH-regulated morphological transition in Candida albicans
More LessSummary: Yeast cells of Candida albicans produced germ tubes in a salt-glucose medium containing 4% calf serum at pH 7 and 37 °C. Hyphal growth continued for 24 h and the filaments did not revert to yeast cells. When cells were grown at pH 4, reversion to yeast growth was observed, despite the presence of serum. The elongation of hyphae was inhibited within 30 min. The distribution of microtubules and microfilaments during pH-regulated morphological transition was studied by an immunofluorescence technique using an antitubulin antibody with a FITC-conjugated secondary antibody, and by staining with tetramethylrhodaminyl phalloidin for filamentous actin and actin granules. After changing to acidic conditions, microtubules were distributed normally in the cytoplasm; however, microfilaments disappeared from hyphal cells, and actin granules were localized at the site of budding. These results show that microfilaments play an important role during pH-regulated morphological transition.
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- Environmental Microbiology
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Plasmids isolated from the sugar beet phyllosphere show little or no homology to molecular probes currently available for plasmid typing
More LessSummary: From a representative sample of bacteria, isolated from mature sugar beet leaves (Beta vulgaris) grown at three separate locations in the UK, 79 (18%) were shown to contain plasmids ranging in size from 10 kb to 200 kb. A sensitive colony blot method was developed to facilitate the screening of both Gram-negative and Gram-positive isolates to determine the distribution of known plasmid incompatibility groups among plasmids isolated from the natural environment using the collection of inc/rep probes derived from basic replicons [rep FIA, FIIA, FIB, HI1, HI2, I1, B/O, L/M, N, P, Q, U, W and X, as described by Couturier et al. (1988) Microbiol Rev 52, 375-395]. After hybridization with each of the radiolabeled replicon probes, 54 of these 79 plasmid-containing natural isolates, which included Erwinia spp., Pseudomonas spp. and Gram-positive bacteria, failed to react. Reactivity was observed with 25 of the 29 Klebsiella and Erwinia isolates investigated. Of the plasmid-containing Enterobacteriaceae examined, 18 reacted with the repFIB probe, six with the repFIIA probe and one isolate, Erwinia salicis SBN169, hybridized to both. Southern hybridization demonstrated that the different isolates which shared homology with the repFIB probe contained a common 1 kb PstI fragment. By comparing the Pstl restriction fragment patterns of total plasmid DNA, the Erwinia and Klebsiella isolates were divided into 10 distinct groups and the other non-reactive isolates divided into a further 24 groups. Plasmid type appeared to be restricted to the geographical location from which the host bacteria were isolated. This study illustrates that sugar beet phyllosphere bacteria support a diverse array of plasmids which cannot be readily classified at the molecular level into the recognized incompatibility groups commonly described for clinical isolates.
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- Genetics And Molecular Biology
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Isolation and characterization of a hydrogen peroxide resistant mutant of Bacillus subtilis
More LessSummary: A mutant of Bacillus subtilis has been isolated by continuous selection in increasing concentrations of H2O2. It grew with a doubling time of 85 min in minimal medium containing 150 mM H2O2, whereas the wild-type parent lysed in 100 mM H2O2. The mutant was also more resistant to organic peroxides than the wild-type. Further resistance to H2O2 could not be induced by pretreatment with low concentrations of the oxidant. The mutant synthesized a number of proteins at a much higher rate than the wild-type, including constitutive synthesis of all of the proteins which were induced by H2O2 in the wild-type. Four of these proteins were sequenced; three were identified as catalase and two subunits of alkyl hydroperoxide reductase. Two proteins whose synthesis was repressed in the mutant were sequenced, and one was identified as flagellin. The mutant grew as non-flagellated, partially septate, filaments of cells, and fragments of flagella were seen in the surrounding medium.
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Transformation of Bacillus licheniformis protoplasts by plasmid DNA
More LessSummary: A simple and efficient protoplast regeneration and PEG-induced transformation procedure was developed for Bacillus licheniformis. The protoplast stabilizing osmoticum was 0.5 M sucrose in the regenerating media, and the restoration of cell wall was carried out at pH 8.4. The mean frequency of regeneration was 83%. The transformation efficiency was studied with four different strains and five plasmids, and ranged from 3.5×105to 7.2×106transformants per μg plasmid DNA depending on the plasmid, and on the donor and recipient strains used. Endonuclease digested and ligated plasmid DNA could also be used to transform the protoplasts, but at a lower frequency.
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Cloning and expression in Escherichia coli of a Streptomyces coelicolor A3 (2) argCJB gene cluster
More LessSummary: From a partial Sau3AI library of Streptomyces coelicolor A3(2) DNA in pIJ916, two hybrid plasmids pGX1 and pGX2 were isolated that complemented S. coelicolor A3(2) or S. lividans arginine auxotrophs. Subcloning DNA from pGX1 in the Escherichia coli expression vector pRK9 containing the Serratia marcescens trp promoter gave rise to one plasmid, pZC2, that complemented E. coli argB, C, E and H auxotrophs, and another, pZC1, that complemented only the first three. The plasmids were markedly unstable in the various complemented hosts, to varying extents; pZC1 was characterized further as providing the stablest host/plasmid combinations. In vitro deletion of part of the vector's trp promoter did not affect complementation of the argB and C auxotrophs, implying that the S. coelicolor A3(2) arg genes may be expressed from their own promoter. The trp promoter-less plasmids included isolates, such as pZC177, that had suffered extensive further deletion without loss of complementing ability. Extracts of an E. coli argE auxotroph carrying pZC177 showed ornithine acetyltransferase activity, indicating that the complementing gene is of the argJ type. The complementation properties of in vitro deletion derivatives of pZC177 indicated the gene order argC-J-B. Part of argC and the upstream region were sequenced; an ORF was identified whose predicted product showed appreciable homology with the E. coli and Bacillus subtilis ArgC polypeptide. Upstream of this ORF a consensus-type promoter and ribosome binding site could be discerned; overlapping its promoter was a sequence with homology to arginine operators in these two other organisms. An in vitro frameshift in argC had a polar effect on expression in E. coli of argJ and B, suggesting that the three genes are transcribed in the same direction, possibly as an operon.
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The catechol 2,3-dioxygenase gene of Rhodococcus rhodochrous CTM: nucleotide sequence, comparison with isofunctional dioxygenases and evidence for an active-site histidine
More LessSummary: In cell-free extracts of Escherichia coli clones harbouring the 3.5 kb BglII fragment of plasmid pTC1 from Rhodococcus rhodochrous CTM a catechol 2,3-dioxygenase (C230) accepting both 3-methylcatechol and 2,3-dihydroxy-biphenyl as substrates could be detected. The plasmid-encoded gene for C230 of R. rhodochrous CTM and its flanking regions were sequenced. In front of the gene a sequence resembling an E. coli promoter was identified, which led to constitutive expression of the cloned gene in E. coli TG1. The derived amino acid sequence of the C230 was compared to that of nine other enzymes, which all catalyse the extradiol cleavage of an aromatic ring. These nine sequences were from different Pseudomonas strains, in contrast to the sequence described here, from a Gram-positive bacterium. The role of four strongly conserved histidines was examined by chemical modification of the histidyl residues of the native enzyme by diethylpyrocarbonate. For that purpose the C230 was purified to homogeneity from E. coli harbouring pSC1701. However, the enzyme lost its activity during the purification. Activity could partially be restored by treatment with Fe2+and reducing agents.
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Analysis of the gene cluster encoding carotenoid biosynthesis in Erwinia herbicola Eho13
Summary: Erwinia herbicola is known to synthesize carotenoids and gives an orange-coloured phenotype. These carotenoids play a role in the protection of the cells from the damage caused by near-UV irradiation in nature. The genes encoding these carotenoids in E. herbicola Eho13 are clustered in a 7 kb DNA fragment. The complete sequence of this fragment has been determined. DNA sequence analysis revealed that the entire sequence contains at least five genes, which are transcribed in the same direction. These five genes are organized in the order crtE-crtX-crtY-crtI-crtB. A gene fusion study showed that two different regions in this 7 kb gene cluster contain promoter activity. Primer-extension analysis identified two transcription start sites, located 147 bp upstream from the first gene of the cluster, crtE, and within the last gene of the cluster, crtB. An RNA-PCR study suggested that the five crt genes were organized in an operon and were transcribed from the promoter upstream from crtE.
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Regulatory circuits involved with pH-regulated gene expression in Salmonella typhimurium
Summary: Salmonella typhimurium encounters a variety of acid conditions during both its natural and pathogenic existence. The ability of this organism to respond transcriptionally to low pH is an area of active interest but little knowledge. As part of an ongoing investigation of low-pH adaptation, 18 pH-controlled IacZ operon fusions in Salmonella typhimurium have been identified (15 in this study) and categorized into at least 11 different loci. They include iroA (at 57 min), aciA (99 min), aciB (90-93 min), aciD (ompC, 45 min), aciJ, aciK(33-36 min), aniC (93 min), anil (33-36 min), hyd (59 min), cadA (54 min) and aniG (63 min). All but two were induced by low pH. One of the exceptions, the iron-regulated iroA locus, was induced at high pH. The unusual aciA locus was induced by low pH under semiaerobic conditions but high pH under aerobic conditions. Most of the other aci genes were expressed best under anaerobic conditions. Many of these genes exhibited strict co-inducer requirements for small molecules to be expressed in minimal medium. These included iron for iroA, tyrosine for aniC, I and aciK, mannose for aniG, formate for hyd, lysine for cadA, and unknown components of complex medium for aciA, aciB and aciD. Six regulatory circuits were revealed involving at least five regulatory loci (fur, oxrG, earAB, earC and ompR). As part of the adaptive response to low pH, S. typhimurium will induce an acid protection system called the acid tolerance response (ATR). As has been shown for fur mutations, the oxrG regulatory mutation interfered with the normal induction of this system.
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Identification and analysis of the Saccharomyces cerevisiae SYR1 gene reveals that ergosterol is involved in the action of syringomycin
Summary: A 2.5 kb DNA fragment of the Saccharomyces cerevisiae SYR1 gene was cloned by complementation of the syr1 mutations that simultaneously lead to resistance to the phytotoxin syringomycin and sensitivity of growth to high Ca2+concentrations. Sequencing of this fragment revealed a single open reading frame encoding a polypeptide of 365 amino acids. Four hydrophobic regions each separated by hydrophilic regions were present in the protein. SYR1 was identical to ERG3, which is suggested to encode C-5 sterol desaturase required for ergosterol biosynthesis. The protein product of SYR1 was identified by Western blot analysis as a protein of 40 kDa in the particulate fraction. Gene disruption experiments demonstrated that elimination of SYR1/ERG3 is not lethal, but results in membrane C-5 desaturated sterol deficiencies, resistance to syringomycin and sensitivity to high Ca2+. The syr1 mutant cells had significantly decreased ability for syringomycin binding. The results indicated that C-5 desaturated sterols are involved in the binding of syringomycin to the cell, and the lack of the sterols in the mutant membrane results in sensitivity to high Ca2+and an increased rate of cellular Ca2+influx.
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Cloning and sequencing of sakP encoding sakacin P, the bacteriocin produced by Lactobacillus sake LTH 673
More LessSummary: Sakacin P is a heat-stable, unmodified peptide bacteriocin produced by Lactobacillus sake LTH 673. The strain was isolated from fermented dry sausages and is well adapted to this habitat. The bacteriocin inhibits the growth of the opportunistic food pathogens Enterococcus faecalis and Listeria monocytogenes and therefore, it may improve the hygienic status of fermented food, i.e. meat products. Oligonucleotide probes were designed from the N-terminal amino acid sequence of sakacin P and used to identify sakP, the structural gene of sakacin P, on the chromosome of L. sake LTH 673. SakP was cloned into Escherichia coli NM554 and the nucleotide sequence of the gene and its adjacent regions were determined. Sakacin P appears to be synthesized as a prepeptide of 61 amino acids which is proteolytically processed to the mature bacteriocin consisting of 43 amino acids. Sequencing of the cloned fragment also revealed the presence of two other open reading frames orfX and orfY, which are located upstream and downstream of sakP, respectively, putatively encoding proteins of 52 and 98 amino acids, respectively. The functions of both ORFs remain unknown. Primer extension analysis revealed a promoter upstream of sakP. Two transcripts of approximately 0.35 and 1.0 kb were detected by Northern hybridization encoding either only sakP, or both sakP and orfY, respectively.
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Stability and function of the signal peptide of the pCloDF13-derived bacteriocin release protein
Summary: The pCloDF13-derived bacteriocin release protein (BRP) is synthesized as a prelipoprotein with a signal peptide which remains stable after processing. This signal peptide accumulates in the cytoplasmic membrane and is, together with the mature BRP, required for efficient release of cloacin DF13. We investigated the structural requirements for stability of the BRP signal peptide by constructing hybrid signal peptides consisting of parts of the BRP and Lpp signal peptides. Signal peptide stability was investigated by pulse-labelling and pulse-chase experiments. To study the functioning of the BRP signal peptide, the hybrid constructs were tested for their ability to promote BRP-mediated cloacin DF13-release and their ability to affect the viability of the host cells. The results obtained suggest that the N-terminal part of the BRP signal peptide together with the C-terminal alanine residue are important for stability. When expressed as a separate entity, all mutant signal peptides that contain a part of the BRP signal peptide are capable of affecting cell viability. The results indicated a possible correlation between stability of the BRP signal peptide and cloacin DF13-release.
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Molecular characterization of a 40 kDa OmpC-like porin from Serratia marcescens
More LessSummary: An oligonucleotide that encodes the N-terminal portion of a 41 kDa porin of Serratia marcescens was used to probe S. marcescens UOC-51 genomic DNA. An 11 kb EcoRI fragment which hybridized with the oligonucleotide was subcloned into Escherichia coli, examined for expression, and sequenced. The product expressed by the cloned gene was 40 kDa. The nucleotide sequence has an ORF of 1.13 kb. When the deduced amino acid sequence was aligned and compared to other enterobacterial porins the cloned S. marcescens porin most closely resembled E. coli OmpC. Although we did not detect osmoregulation or thermoregulation of any porins in S. marcescens UOC-51, sequences analogous to the E. coli osmoregulator OmpR-binding regions are seen upstream to the cloned gene. We examined the regulation of the S. marcescens porin in E. coli and found that its expression increased in a high salt environment. A micF gene, whose transcriptional product functions to inhibit synthesis of OmpF by hybridizing with the ompF transcript, was also seen upstream of the S. marcescens ompC. An alignment with the E. coli micF gene revealed that the functional region of the S. marcescens micF gene is conserved. Based on the results obtained we have determined that S. marcescens UOC-51 produces a 40 kDa porin similar to the E. coli OmpC porin.
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- Pathogenicity And Medical Microbiology
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Phagocytosis by pig alveolar macrophages of Actinobacillus pleuropneumoniae serotype 2 mutant strains defective in haemolysin II (Apxll) and pleurotoxin (ApxIII)
More LessSummaryThe ability of pig alveolar macrophages to phagocytose Actinobacillus pleuropneumoniae HK 361, which produces both haemolysin II (Apxlll) and pleurotoxin (Apxlll), has been studied. Macrophages incubated with HK 361 in the presence of normal pig serum were rapidly killed. Incubation of the macrophages with a haemolysin-deficient mutant (HK 361 e), which possesses only cytotoxic activity (Apxlll), also caused gross damage to the macrophages. A mutant (HK 361 h) which produces neither Apxll nor Apxlll in its culture supernatant allowed longer survival of the macrophages than did either the parent strain or mutant e when incubated with normal pig serum. Prolonged incubation with mutant h resulted in an increase in the number of damaged macrophages, but not to the same extent as with either HK 361 or mutant e. The number of mutant h cells phagocytosed in the presence of normal pig serum was low. The addition of either hyperimmune rabbit serum, raised against whole formalin-treated HK 361 cells, or convalescent pig serum from a pig recovering from a serotype 3 infection, which contained antibody against both Apxll and Apxlll, did not increase the survival of macrophages incubated with either HK 361 or mutant e. However, incubation of mutant h with convalescent pig serum did result in damage-free macrophages. This serum, which possessed neutralizing capabilities against the toxic activities of Apxll and Apxlll, enhanced the number of mutant h cells phagocytosed compared to the numbers phagocytosed in normal pig serum. Killed bacteria were rapidly phagocytosed and did not damage macrophages. The number of phagocytosed killed bacteria appeared to be similar to that seen with live mutant h cells when incubated in the presence of convalescent pig serum. The presence of a toxic activity associated with the haemolysin-and cytotoxin-negative mutant may represent an additional cell-associated toxin which is not present in its culture supernatant. It appears therefore, that in the absence of extracellular Apxll and Apxlll and in the presence of convalescent pig serum A. pleuropneumoniae is readily phagocytosed.
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A new assay for the invasive adenylate cyclase toxin of Bordetella pertussis based on its morphological effects on the fibronectinstimulated spreading of BHK21 cells
SummaryWhen baby hamster kidney (BHK) cells are allowed to spread on fibronectincoated substrata in the absence of serum and the presence of agents which elevate intracellular 3’:5’-cyclic AMP (cAMP) levels they adopt an abnormal, stellated morphology. To determine whether the invasive adenylate cyclase (AC) toxin of Bordetella pertussis induced the same response, cell extracts were prepared from several B. pertussis strains. They were characterized for AC toxin production by enzymic assay and by immunobiotting with an AC-toxin-specific monoclonal antibody. Extracts of strains producing AC toxin induced elevated levels of intracellular cAMP in BHK cells and promoted a stellation response during cell spreading. Extracts prepared from strains defective in AC toxin production showed no effect. Using image analysis to quantify the morphological change, we have demonstrated that the effect of AC toxin on cell spreading is dose dependent. This technique is a rapid and sensitive assay for the invasive AC toxin.
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Isolation and characterization of Bordetella parapertussis-like bacteria from ovine lungs
More LessSummaryBacteria resembling two Bordetella species were isolated from both normal and pneumonic ovine lungs using a selective charcoal agar. Twenty-eight of the 33 isolates showed similarities to stock NCTC B. parapertussis strains in their SDS-PAGE gel protein profiles, in their biochemical reactions and in causing browning on tyrosine agar. Five isolates behaved similarly to stock B. bronchiseptica strains, in being actively motile, in giving identical positive reactions in three out of four biochemical tests and in causing no colour change in tyrosine agar. Multilocus enzyme electrophoresis separated the isolates into two electrophoretic types distinguishable from those of stock B. parapertussis and stock B. bronchiseptica strains.
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- Physiology And Growth
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Organization and regulation of the mitochondrial oxidative pathway in Mucor rouxii
More LessSummary: Mitochondria from spores, anaerobic yeasts and aerobic mycelium of Mucor rouxii were isolated and the components of the respiratory pathways were analysed. Our data suggest the presence in these mitochondria of three different NADH dehydrogenases, three b- and two c-type cytochromes, plus three different terminal oxidases: cytochrome c oxidase, an incompletely characterized cytochrome which, by its spectral characteristics, behaves as a cytochrome o, and a salicylhydroxamic-acid-sensitive oxidase. The composition of the respiratory chain, as well as the relative proportions of cytochromes and oxidases in the mitochondria, were distinct at each developmental stage. Our data suggest that the development of the respiratory pathways during differentiation is mainly regulated by the oxygen tension. Besides this role, oxygen also influences the relative number of mitochondria in the cells and their ultrastructural organization.
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Anaerobic degradation of pimelate by newly isolated denitrifying bacteria
More LessSummary: A C7 dicarboxylic (pimelic) acid derivative is postulated as an intermediate in anaerobic degradation of benzoate. Four strains of Gram-negative, nitrate-reducing bacteria capable of growth with both pimelate and benzoate as sole carbon and energy source were isolated. The metabolism of strain LP-1, which was enriched from activated sludge with pimelate as substrate, was studied in detail. This strain grew only with oxygen or with oxidized nitrogen compounds as electron acceptor. In the presence of nitrate, a wide range of substrates excluding C1 compounds was degraded. The new isolate was catalase- and oxidase-positive, and had one single polar flagellum. Strain LP-1 was tentatively classified within the family Pseudomonadaceae. The catabolism of pimelate and benzoate was studied in cell-free extracts of strain LP-1. Both acids were activated with coenzyme A in a Mg2+- and ATP-dependent reaction. The corresponding acyl-CoA synthetases were specifically induced by the respective growth substrate. Pimelate was also activated by CoA transfer from succinyl-CoA. Pimelyl-CoA was oxidized by cell-free extracts in the presence of potassium ferricyanide. Degradation to glutaryl-CoA and acetyl-CoA proceeded by a sequence of β-oxidation-like reactions. Glutaryl-CoA dehydrogenase and glutaconyl-CoA decarboxylase activities were expressed in cells grown with pimelate or benzoate, indicating the specific involvement of these enzyme activities in anaerobic degradation of these two acids. Enzyme activities responsible for further degradation of the resulting crotonyl-CoA to acetyl-CoA via classical β-oxidation were also detected.
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Volume 50 (1968)
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Volume 49 (1967)
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Volume 48 (1967)
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Volume 47 (1967)
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Volume 46 (1967)
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Volume 45 (1966)
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Volume 44 (1966)
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Volume 43 (1966)
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Volume 42 (1966)
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Volume 41 (1965)
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Volume 40 (1965)
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Volume 39 (1965)
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Volume 38 (1965)
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Volume 37 (1964)
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Volume 36 (1964)
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Volume 35 (1964)
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Volume 34 (1964)
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Volume 33 (1963)
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Volume 32 (1963)
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Volume 31 (1963)
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Volume 30 (1963)
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Volume 29 (1962)
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Volume 28 (1962)
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Volume 27 (1962)
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Volume 26 (1961)
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Volume 25 (1961)
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Volume 24 (1961)
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Volume 23 (1960)
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Volume 22 (1960)
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Volume 21 (1959)
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Volume 20 (1959)
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Volume 19 (1958)
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Volume 18 (1958)
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Volume 17 (1957)
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Volume 16 (1957)
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Volume 15 (1956)
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Volume 14 (1956)
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Volume 13 (1955)
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Volume 12 (1955)
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Volume 11 (1954)
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Volume 10 (1954)
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Volume 9 (1953)
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Volume 8 (1953)
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Volume 7 (1952)
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Volume 6 (1952)
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Volume 5 (1951)
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Volume 4 (1950)
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Volume 3 (1949)
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Volume 2 (1948)
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Volume 1 (1947)