General Biology and Physiology

Mitchell, Wilfrid J.

doi:10.1002/3527600108.ch3

Cited by 14 publications

(8 citation statements)

References 307 publications

(417 reference statements)

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“…In some clostridial species, for example, C. perfringens, toxins are produced in association with sporulation (18). However, it has been shown that in C. botulinum, the highest levels of toxin production are generally found in cells undergoing rapid autolysis, which do not sporulate (7,29).…”

Section: Discussionmentioning

confidence: 99%

Regulation of Neurotoxin Production and Sporulation by a Putative agrBD Signaling System in Proteolytic Clostridium botulinum

Cooksley

Davis

Winzer

et al. 2010

Appl Environ Microbiol

115

104

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A significant number of genome sequences of Clostridium botulinum and related species have now been determined. In silico analysis of these data revealed the presence of two distinct agr loci (agr-1 and agr-2) in all group I strains, each encoding putative proteins with similarity to AgrB and AgrD of the well-studied Staphylococcus aureus agr quorum sensing system. In S. aureus, a small diffusible autoinducing peptide is generated from AgrD in a membrane-located processing event that requires AgrB. Here the characterization of both agr loci in the group I strain C. botulinum ATCC 3502 and of their homologues in a close relative, Clostridium sporogenes NCIMB 10696, is reported. In C. sporogenes NCIMB 10696, agr-1 and agr-2 appear to form transcriptional units that consist of agrB, agrD, and flanking genes of unknown function. Several of these flanking genes are conserved in Clostridium perfringens. In agreement with their proposed role in quorum sensing, both loci were maximally expressed during late-exponential-phase growth. Modulation of agrB expression in C. sporogenes was achieved using antisense RNA, whereas in C. botulinum, insertional agrD mutants were generated using ClosTron technology. In comparison to the wild-type strains, these strains exhibited drastically reduced sporulation and, for C. botulinum, also reduced production of neurotoxin, suggesting that both phenotypes are controlled by quorum sensing. Interestingly, while agr-1 appeared to control sporulation, agr-2 appeared to regulate neurotoxin formation.

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Section: Discussionmentioning

confidence: 99%

Regulation of Neurotoxin Production and Sporulation by a Putative agrBD Signaling System in Proteolytic Clostridium botulinum

Cooksley

Davis

Winzer

et al. 2010

Appl Environ Microbiol

115

104

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“…O'Brien and Morris proposed that NAD(P)H oxidation systems react with oxygen to cause oxidation of the electron donor, i.e., NAD(P)H, which is required for the central pathway for anaerobic metabolism; this then leads to the eventual inability of clostridia to maintain their internal redox balance (51,55). However, many questions remain about the mechanisms of aerobic growth inhibition in clostridia (50).…”

mentioning

confidence: 99%

Adaptive Responses to Oxygen Stress in Obligatory Anaerobes Clostridium acetobutylicum and Clostridium aminovalericum

Kawasaki

Watamura

Ono

et al. 2005

Appl Environ Microbiol

102

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Clostridium acetobutylicum and Clostridium aminovalericum, both obligatory anaerobes, grow normally after growth conditions are changed from anoxic to microoxic, where the cells consume oxygen proficiently. In C. aminovalericum, a gene encoding a previously characterized H 2 O-forming NADH oxidase, designated noxA, was cloned and sequenced. The expression of noxA was strongly upregulated within 10 min after the growth conditions were altered to a microoxic state, indicating that C. aminovalericum NoxA is involved in oxygen metabolism. In C. acetobutylicum, genes suggested to be involved in oxygen metabolism and genes for reactive oxygen species (ROS) scavenging were chosen from the genome database. Although no clear orthologue of C. aminovalericum NoxA was found, Northern blot analysis identified many O 2 -responsive genes (e.g., a gene cluster [CAC2448 to CAC2452] encoding an NADH rubredoxin oxidoreductase-A-type flavoprotein-desulfoferrodoxin homologue-MerR family-like protein-flavodoxin, an operon [CAC1547 to CAC1549] encoding a thioredoxin-thioredoxin reductase-glutathione peroxidase-like protein, an operon [CAC1570 and CAC1571] encoding two glutathione peroxidase-like proteins, and genes encoding thiol peroxidase, bacterioferritin comigratory proteins, and superoxide dismutase) whose expression was quickly and synchronously upregulated within 10 min after flushing with 5% O 2. The corresponding enzyme activities, such as NAD(P)H-dependent peroxide (H 2 O 2 and alkyl hydroperoxides) reductase, were highly induced, indicating that microoxic growth of C. acetobutylicum is associated with the expression of a number of genes for oxygen metabolism and ROS scavenging.Bacteria belonging to the genus Clostridium are classified as obligatory anaerobes (26,62) and are widely used in the field of solvent fermentation, biodegradation, and microbial energy production. Oxygen has a crucial effect on the growth of clostridia, but the mechanisms of growth inhibition, as well as the existence of O 2 metabolic systems, remain unknown. Some hypotheses to explain aerobic growth inhibition in anaerobes were proposed, such as the possibility that oxygen attacks oxygen-sensitive enzymes causing metabolic cessation or that anaerobes lack the ability to decompose active oxygen species, such as catalase, which cause irreversible oxidative damage to DNA and lipid molecules (2,27,49,63,67). O'Brien and Morris proposed that NAD(P)H oxidation systems react with oxygen to cause oxidation of the electron donor, i.e., NAD(P)H, which is required for the central pathway for anaerobic metabolism; this then leads to the eventual inability of clostridia to maintain their internal redox balance (51, 55). However, many questions remain about the mechanisms of aerobic growth inhibition in clostridia (50).Most Clostridium species do not form colonies in the presence of 1% oxygen (2, 62); however, they can accept microoxic conditions when grown in liquid medium (32-35, 39, 51, 55). Based on physiological examination, clostridia possess systems to met...

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“…Notably, amplicon 11 was identified to originate from Clostridium , which is known to be an anaerobic nitrogen fixer (Choudhury and Kennedy ; Minamisawa et al . ; Mitchell ), and amplicon 15 was identified to originate from Massilia , a genus that contains an obligate aerobic environmental bacterium of the subclass Betaproteobacteria.…”

Section: Resultsmentioning

confidence: 99%

Investigation of the mechanisms underlying the high acetylene-reducing activity exhibited by the soil bacterial community from BC2 horizon in the permafrost zone of the East Siberian larch forest bed

2014

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Aims: This study addressed a microbial composition of East Siberian larch forest bed soil and focused on major nitrogen-fixing bacterial consortia showing the highest capacity to induce acetylene reduction. Methods and Results: The ability of a soil microbial consortium to effectively reduce acetylene was investigated using gellan gum medium. In parallel, each microbial component in the medium was analysed by a 16S rRNA genetargeting denaturing gradient gel electrophoresis (DGGE), together with an attempt to isolate pure culture of the culturable eubacteria. Six strains of the isolated bacteria were characterized as diazotrophs, and Burkholderia xenovorans was found to be one of the major nitrogen fixer in the bacterial community cultured from the BC2 horizon soil microbiota. Co-culturing of either a diazotrophic Pseudomonas sp. with a nondiazotrophic Luteibacter sp. or a diazotrophic Luteibacter sp. with a nondiazotrophic bacterium B. xenovorans resulted in a marked elevation in acetylene reduction over that observed in the pure culture of each diazotroph. Conclusions: A promotion of acetylene reduction in mixed bacterial cultures, particularly when the cultures included Luteibacter, was clearly observed due to an increase in the bacterial cell population. Significance and Impact of the Study: Our study, which showed that some unculturable bacteria including anaerobic Clostridium sp. that can provide major contribution to nitrogen fixation, may provide key information useful in identifying the 'missing link' in the nitrogen cycle in the cryogenic soil ecosystem of boreal forests.

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General Biology and Physiology

Cited by 14 publications

References 307 publications

Regulation of Neurotoxin Production and Sporulation by a Putative agrBD Signaling System in Proteolytic Clostridium botulinum

Regulation of Neurotoxin Production and Sporulation by a Putative agrBD Signaling System in Proteolytic Clostridium botulinum

Adaptive Responses to Oxygen Stress in Obligatory Anaerobes Clostridium acetobutylicum and Clostridium aminovalericum

Investigation of the mechanisms underlying the high acetylene-reducing activity exhibited by the soil bacterial community from BC2 horizon in the permafrost zone of the East Siberian larch forest bed

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