A peroxide/ascorbate-inducible catalase from Haemophilus influenzae is homologous to the Escherichia coli katE gene product

Investigating catalase activity through hydrogen peroxide decomposition by bacteria biofilms in real time using scanning electrochemical microscopy

Catalase activity through hydrogen peroxide decomposition in a 1 mM bulk solution above Vibrio fischeri (γ-Protebacteria-Vibrionaceae) bacterial biofilms of either symbiotic or free-living strains was studied in real time by scanning electrochemical microscopy (SECM). The catalase activity, in units of micromoles hydrogen peroxide decomposed per minute over a period of 348 s, was found to vary with incubation time of each biofilm in correlation with the corresponding growth curve of bacteria in liquid culture. Average catalase activity for the same incubation times ranging from 1 to 12 h was found to be 0.28 ± 0.07 μmol H2O2/min for the symbiotic biofilms and 0.31 ± 0.07 μmol H2O2/min for the free-living biofilms, suggesting similar catalase activity. Calculations based on Comsol Multiphysics simulations in fitting experimental biofilm data indicated that approximately (3 ± 1) × 10(6) molecules of hydrogen peroxide were decomposed by a single bacterium per second, signifying the presence of a highly active catalase. A 2-fold enhancement in catalase activity was found for both free-living and symbiotic biofilms in response to external hydrogen peroxide concentrations as low as 1 nM in the growth media, implying a similar mechanism in responding to oxidative stress.

Haemophilus influenzae and oxidative stress

Haemophilus influenzae is a commensal of the human upper respiratory tract. H. influenzae can, however, move out of its commensal niche and cause multiple respiratory tract diseases. Such diseases include otitis media in young children, as well as exacerbations of chronic obstructive pulmonary disease (COPD), sinusitis, conjunctivitis, and bronchitis. During the course of colonization and infection, H. influenzae must withstand oxidative stress generated by multiple reactive oxygen species produced endogenously, by other co-pathogens and by host cells. H. influenzae has, therefore, evolved multiple mechanisms that protect the cell against oxygen-generated stresses. In this review, we will describe these systems relative to the well-described systems in Escherichia coli. Moreover, we will compare how H. influenzae combats the effect of oxidative stress as a necessary phenotype for its roles as both a successful commensal and pathogen.

Human catalase: looking for complete identity

Catalases are well studied enzymes that play critical roles in protecting cells against the toxic effects of hydrogen peroxide. The ubiquity of the enzyme and the availability of substrates made heme catalases the focus of many biochemical and molecular biology studies over 100 years. In human, this has been implicated in various physiological and pathological conditions. Advancement in proteomics revealed many of novel and previously unknown features of this mysterious enzyme, but some functional aspects are yet to be explained. Along with discussion on future research area, this mini-review compile the information available on the structure, function and mechanism of action of human catalase.

Bacillus subtilis Vegetative Catalase Is an Extracellular Enzyme

Strong catalase activity was secreted by Bacillus subtilis cells during stationary growth phase in rich medium but not in sporulation-inducing medium. N-terminal sequencing indicated that the secreted activity was due to the vegetative catalase KatA, previously considered an endocellular enzyme. Extracellular catalase protected B. subtilis cells from oxidative assault.

The OxyR regulon in nontypeable Haemophilus influenzae

Nontypeable Haemophilus influenzae (NTHi) is a gram-negative bacterium and a common commensal organism of the upper respiratory tract in humans. NTHi causes a number of diseases, including otitis media, sinusitis, conjunctivitis, exacerbations of chronic obstructive pulmonary disease, and bronchitis. During the course of colonization and infection, NTHi must withstand oxidative stress generated by insult due to multiple reactive oxygen species produced endogenously by other copathogens and by host cells. Using an NTHi-specific microarray containing oligonucleotides representing the 1821 open reading frames of the recently sequenced NTHi isolate 86-028NP, we have identified 40 genes in strain 86-028NP that are upregulated after induction of oxidative stress due to hydrogen peroxide. Further comparisons between the parent and an isogenic oxyR mutant identified a subset of 11 genes that were transcriptionally regulated by OxyR, a global regulator of oxidative stress. Interestingly, hydrogen peroxide induced the OxyR-independent upregulation of expression of the genes encoding components of multiple iron utilization systems. This finding suggested that careful balancing of levels of intracellular iron was important for minimizing the effects of oxidative stress during NTHi colonization and infection and that there are additional regulatory pathways involved in iron utilization.

Oxidative stress in bacterial meningitis

Fifty years after the advent of antibiotics for clinical use, the rates of morbidity and mortality associated with bacterial meningitis remain high. The unfavourable clinical outcome is often due to intracranial complications including cerebrovascular insults, raised intracranial pressure, hydrocephalus, and brain edema. Reactive oxygen species (ROS) are known effector molecules in the antimicrobial armature of polymorphonuclear and mononuclear phagocytes. However, over the last decade, there has been a substantial body of work implicating a central role of ROS in the development of intracranial complications and brain damage in bacterial meningitis. Recently, it also became evident that reactive nitrogen species (RNS), especially nitric oxide, are important mediators of meningitis-associated pathophysiological changes, at least during the early phase of the disease. There is now substantial evidence that much of the oxidative injury associated by simultaneous production of superoxide and nitric oxide is mediated by the strong oxidant peroxynitrite. ROS and peroxynitrite can be cytotoxic via a number of independent mechanisms. Their cytotoxic effects include initiation of lipid peroxidation and induction of DNA single strand breakage. Damaged DNA activates poly(ADP-ribose) polymerase (PARP). Recent experimental data propose a role of lipid peroxidation and PARP activation in the development of meningitis-associated intracranial complications and brain injury. Agents which interfere with the production of ROS and peroxynitrite, as well as with PARP activation and lipid peroxidation may represent novel, therapeutic strategies to limit meningitis-associated brain damage, and, thus, to improve the outcome of this serious disease.

Genomic sequence of an otitis media isolate of nontypeable Haemophilus influenzae: comparative study with H. influenzae serotype d, strain KW20

In 1995, the Institute for Genomic Research completed the genome sequence of a rough derivative of Haemophilus influenzae serotype d, strain KW20. Although extremely useful in understanding the basic biology of H. influenzae, these data have not provided significant insight into disease caused by nontypeable H. influenzae, as serotype d strains are not pathogens. In contrast, strains of nontypeable H. influenzae are the primary pathogens of chronic and recurrent otitis media in children. In addition, these organisms have an important role in acute otitis media in children as well as other respiratory diseases. Such strains must therefore contain a gene repertoire that differs from that of strain Rd. Elucidation of the differences between these genomes will thus provide insight into the pathogenic mechanisms of nontypeable H. influenzae. The genome of a representative nontypeable H. influenzae strain, 86-028NP, isolated from a patient with chronic otitis media was therefore sequenced and annotated. Despite large regions of synteny with the strain Rd genome, there are large rearrangements in strain 86-028NP's genome architecture relative to the strain Rd genome. A genomic island similar to an island originally identified in H. influenzae type b is present in the strain 86-028NP genome, while the mu-like phage present in the strain Rd genome is absent from the strain 86-028NP genome. Two hundred eighty open reading frames were identified in the strain 86-028NP genome that were absent from the strain Rd genome. These data provide new insight that complements and extends the ongoing analysis of nontypeable H. influenzae virulence determinants.

A Neisseria gonorrhoeae catalase mutant is more sensitive to hydrogen peroxide and paraquat, an inducer of toxic oxygen radicals

Catalase is hypothesized to be critical in the protection of Neisseria gonorrhoeae from H2O2 produced during aerobic respiration and by phagocytes during infection. Here we cloned the catalase (kat) gene of gonococcal strain FA1090 and constructed a genetically defined N. gonorrhoeae kat mutant to assess the role of catalase in defense against oxidative stress. The gonococcal kat gene conferred increased H2O2 resistance to a catalase-deficient Escherichia coli strain. Mutation of the kat gene in strain FA1090 via an in-frame deletion resulted in increased sensitivity to H2O2 and paraquat, an inducer of toxic oxygen radicals. Expression of catalase in trans from a shuttle vector restored catalase activity and paraquat resistance to the kat mutant, but not resistance to H2O2. The inability to fully complement the mutant was perhaps due to a modification in the catalase, as evidenced by altered mobility of the recombinant catalase on activity gels when expressed from the shuttle vector in N. gonorrhoeae. Additionally, we showed a 262 base pair region upstream of the kat gene is required for expression in E. coli and a putative fumarate-nitrate regulator (FNR) binding site is located in this region.

Physiological characterization of Haemophilus influenzae Rd deficient in its glutathione-dependent peroxidase PGdx

The chimeric peroxidase PGdx of Haemophilus influenzae Rd belongs to a recently identified family of thiol peroxidases capable of reducing hydrogen peroxide as well as alkylhydroperoxides by means of glutathione redox cycling. In the present study, we constructed a H. influenzae Rd strain, deficient in its PGdx encoding gene (open reading frame HI0572). The mutant was shown by disk inhibition and liquid culture growth assays to exhibit increased susceptibility to organic hydroperoxides. The hampered growth was restored by complementing the interrupted gene on the genome with a replicating plasmid bearing an intact copy of the gene, hereby rejecting the possible influences of polar effects. Elevated levels of hydrogen peroxide scavenging activity, due to the catalase HktE, were measured in the absence of a functional pgdx gene rendering the mutant more resilient against hydrogen peroxide. On the other hand, after initiation of the stationary phase, aerobic cultures of the pgdx mutant were practically devoid of living cells, whereas wild-type counterparts retained viability. This observed feature was alleviated by complementation with the functional gene or with the addition of catalase.

Glutathione and catalase provide overlapping defenses for protection against respiration-generated hydrogen peroxide in Haemophilus influenzae

Glutathione is an abundant and ubiquitous low-molecular-weight thiol that may play a role in many cellular processes, including protection against the deleterious effects of reactive oxygen species. We address here the role of glutathione in protection against hydrogen peroxide (H2O2) in Haemophilus influenzae and show that glutathione and catalase provide overlapping defense systems. H. influenzae is naturally glutathione deficient and imports glutathione from the growth medium. Mutant H. influenzae lacking catalase and cultured in glutathione-deficient minimal medium is completely devoid of H2O2 scavenging activity and, accordingly, substantial amounts of H2O2 accumulate in the growth medium. H. influenzae generates H2O2 at rates similar to those reported for Escherichia coli, but the toxicity of this harmful metabolite is averted by glutathione-based H2O2 removal, which appears to be the primary system for protection against H2O2 endogenously generated during aerobic respiration. When H2O2 concentrations exceed low micromolar levels, the hktE gene-encoded catalase becomes the predominant scavenger. The requirement for glutathione in protection against oxidative stress is analogous to that in higher and lower eukaryotes but is unlike the situation in other bacteria in which glutathione is dispensable for aerobic growth during both normal and oxidative stress conditions.

Purification and characterization of a chimeric enzyme from Haemophilus influenzae Rd that exhibits glutathione-dependent peroxidase activity

While belonging to the same family of antioxidant enzymes, members of the peroxiredoxins do not necessarily employ one and the same method for their reduction. Most representatives become reduced with the aid of thioredoxin, whereas some members use AhpF, tryparedoxin, or cyclophilin A. Recent research on a new peroxiredoxin isoform (type C) from Populus trichocarpa has shown that these particular types may also use glutaredoxin instead of thioredoxin. This finding is supported by the occurrence of chimeric proteins composed of a peroxiredoxin and glutaredoxin region. A gene encoding such a fusion protein is enclosed in the Haemophilus influenzae Rd genome. We expressed the H. influenzae protein, denoted here as PGdx, in Escherichia coli and purified the recombinant enzyme. In vitro assays demonstrate that PGdx, in the presence of dithiothreitol or glutathione, is able to protect supercoiled DNA against the metal ion-catalyzed oxidation-system. Enzymatic assays did, indeed, characterize PGdx as a peroxidase, requiring the glutathione redox cycle for the reduction of hydrogen peroxide (k(cat)/K(m) 5.01 x 10(6) s(-1) m(-1)) as well as the small organic hydroperoxide tert-butylhydroperoxide (k(cat)/K(m) 5.67 x 10(4) s(-1) m(-1)). Enzymatic activity as function of the glutathione concentration deviated from normal Michaelis-Menten kinetics, giving a sigmoidal pattern with an apparent Hill coefficient of 2.9. Besides the formation of a disulfide-linked PGdx dimer, it was also shown by mass spectrometric analysis that cysteine 49, which is equivalent to the active site cysteine of the peroxiredoxins, undergoes glutathionylation during purification under nonreducing conditions. Based on these results, we propose a model for the catalytic mechanism.

Exogenous glutathione completes the defense against oxidative stress in Haemophilus influenzae

Since they are equipped with several strategies by which they evade the antimicrobial defense of host macrophages, it is surprising that members of the genus Haemophilus appear to be deficient in common antioxidant systems that are well established to protect prokaryotes against oxidative stress. Among others, no genetic evidence for glutathione (gamma-Glu-Cys-Gly) (GSH) biosynthesis or for alkyl hydroperoxide reduction (e.g., the Ahp system characteristic or enteric bacteria) is apparent from the Haemophilus influenzae Rd genome sequence, suggesting that the organism relies on alternative systems to maintain redox homeostasis or to reduce small alkyl hydroperoxides. In this report we address this apparent paradox for the nontypeable H. influenzae type strain NCTC 8143. Instead of biosynthesis, we could show that this strain acquires GSH by importing the thiol tripeptide from the growth medium. Although such GSH accumulation had no effect on growth rates, the presence of cellular GSH protected against methylglyoxal, tert-butyl hydroperoxide (t-BuOOH), and S-nitrosoglutathione toxicity and regulated the activity of certain antioxidant enzymes. H. influenzae NCTC 8143 extracts were shown to contain GSH-dependent peroxidase activity with t-BuOOH as the peroxide substrate. The GSH-mediated protection against t-BuOOH stress is most probably catalyzed by the product of open reading frame HI0572 (Prx/Grx), which we isolated from a genomic DNA fragment that confers wild-type resistance to t-BuOOH toxicity in the Ahp-negative Escherichia coli strain TA4315 and that introduces GSH-dependent alkyl hydroperoxide reductase activity into naturally GSH peroxidase-negative E. coli. Finally, we demonstrated that cysteine is an essential amino acid for growth and that cystine, GSH, glutathione amide, and cysteinylglycine can be catabolized in order to complement cysteine deficiency.

Role of Acinetobacter calcoaceticus 3,4-dihydrocoumarin hydrolase in oxidative stress defence against peroxoacids

The physiological role of a bifunctional enzyme, 3,4-dihydrocoumarin hydrolase (DCH), which is capable of both hydrolysis of ester bonds and organic acid-assisted bromination of organic compounds, was investigated. Purified DCH from Acinetobacter calcoaceticus F46 catalysed dose- and time-dependent degradation of peracetic acid. The gene (dch) was cloned from the chromosomal DNA of the bacterium. The dch ORF was 831 bp long, corresponding to a protein of 272 amino acid residues, and the deduced amino acid sequence showed high similarity to those of bacterial serine esterases and perhydrolases. The dch gene was disrupted by homologous recombination on the A. calcoaceticus genome. The dch disruptant strain was more sensitive to growth inhibition by peracetic acid than the parent strain. On the other hand, the recombinant Escherichia coli cells expressing dch were more resistant to peracetic acid. A putative catalase gene was found immediately downstream of dch, and Northern blot hybridization analysis revealed that they are transcribed as part of a polycistronic mRNA. These results suggested that in vivo DCH detoxifies peroxoacids in conjunction with the catalase, i.e. peroxoacids are first hydrolysed to the corresponding acids and hydrogen peroxide by DCH, and then the resulting hydrogen peroxide is degraded by the catalase.

Feedback regulation of an Agrobacterium catalase gene katA involved in Agrobacterium-plant interaction

Catalases are known to detoxify H2O2, a major component of oxidative stress imposed on a cell. An Agrobacterium tumefaciens catalase encoded by a chromosomal gene katA has been implicated as an important virulence factor as it is involved in detoxification of H2O2 released during Agrobacterium-plant interaction. In this paper, we report a feedback regulation pathway that controls the expression of katA in A. tumefaciens cells. We observed that katA could be induced by plant tissue sections and by acidic pH on a minimal medium, which resembles the plant environment that the bacteria encounter during the course of infection. This represents a new regulatory factor for catalase induction in bacteria. More importantly, a feedback regulation was observed when the katA-gfp expression was studied in different genetic backgrounds. We found that introduction of a wild-type katA gene encoding a functional catalase into A. tumefaciens cells could repress the katA-gfp expression over 60-fold. The katA gene could be induced by H2O2 and the encoded catalase could detoxify H2O2. In addition, the katA-gfp expression of one bacterial cell could be repressed by other surrounding catalase-proficient bacterial cells. Furthermore, mutation at katA caused a 10-fold increase of the intracellular H2O2 concentration in the bacteria grown on an acidic pH medium. These results suggest that the endogenous H2O2 generated during A. tumefaciens cell growth could serve as the intracellular and intercellular inducer for the katA gene expression and that the acidic pH could pose an oxidative stress on the bacteria. Surprisingly, one mutated KatA protein, exhibiting no significant catalase activity as a result of the alteration of two important residues at the putative active site, could partially repress the katA-gfp expression. The feedback regulation of the katA gene by both catalase activity and KatA protein could presumably maintain an appropriated level of catalase activity and H2O2 inside A. tumefaciens cells.

Plasmid-encoded catalase KatA, the main catalase of Pseudomonas fluorescens strain Cb36

The plasmid-state catalase gene katA of the phenol gradative Pseudomonas fluorescens isolate Cb36 has been characterized and shown to be the major catalase of this strain. The predicted amino acid sequence of KatA revealed significant similarity with the catalase sequence from Neisseria meningitidis and has probably the non-pseudomonad origin. The specific activity of catalase was investigated and elevated catalase activity was found in stationary phase cells. The consensus sequence for promoters recognized by the stationary phase sigma factor sigma(s) was found 212 bp upstream of the putative ATG start codon. The ability of KatA to detoxify a high concentration of hydrogen peroxide and protect Pseudomonas putida and Escherichia coli cells was shown.

Purification and characterization of a catalase from the facultatively psychrophilic bacterium Vibrio rumoiensis S-1(T) exhibiting high catalase activity

Catalase from the facultatively psychrophilic bacterium Vibrio rumoiensis S-1(T), which was isolated from an environment exposed to H(2)O(2) and exhibited high catalase activity, was purified and characterized, and its localization in the cell was determined. Its molecular mass was 230 kDa, and the molecule consisted of four identical subunits. The enzyme, which was not apparently reduced by dithionite, showed a Soret peak at 406 nm in a resting state. The catalytic activity was 527,500 U. mg of protein(-1) under standard reaction conditions at 40 degrees C, 1.5 and 4.3 times faster, respectively, than those of the Micrococcus luteus and bovine catalases examined under the same reaction conditions, and showed a broad optimum pH range (pH 6 to 10). The catalase from strain S-1(T) is located not only in the cytoplasmic space but also in the periplasmic space. There is little difference in the activation energy for the activity between strain S-1(T) catalase and M. luteus and bovine liver catalases. The thermoinstability of the activity of the former catalase were significantly higher than those of the latter catalases. The thermoinstability suggests that the catalase from strain S-1(T) should be categorized as a psychrophilic enzyme. Although the catalase from strain S-1(T) is classified as a mammal type catalase, it exhibits the unique enzymatic properties of high intensity of enzymatic activity and thermoinstability. The results obtained suggest that these unique properties of the enzyme are in accordance with the environmental conditions under which the microorganism lives.

Purification and characterization of an iron superoxide dismutase and a catalase from the sulfate-reducing bacterium Desulfovibrio gigas

The iron-containing superoxide dismutase (FeSOD; EC 1.15.1.1) and catalase (EC 1.11.1.6) enzymes constitutively expressed by the strictly anaerobic bacterium Desulfovibrio gigas were purified and characterized. The FeSOD, isolated as a homodimer of 22-kDa subunits, has a specific activity of 1,900 U/mg and exhibits an electron paramagnetic resonance (EPR) spectrum characteristic of high-spin ferric iron in a rhombically distorted ligand field. Like other FeSODs from different organisms, D. gigas FeSOD is sensitive to H(2)O(2) and azide but not to cyanide. The N-terminal amino acid sequence shows a high degree of homology with other SODs from different sources. On the other hand, D. gigas catalase has an estimated molecular mass of 186 +/- 8 kDa, consisting of three subunits of 61 kDa, and shows no peroxidase activity. This enzyme is very sensitive to H(2)O(2) and cyanide and only slightly sensitive to sulfide. The native enzyme contains one heme per molecule and exhibits a characteristic high-spin ferric-heme EPR spectrum (g(y,x) = 6.4, 5.4); it has a specific activity of 4,200 U/mg, which is unusually low for this class of enzyme. The importance of these two enzymes in the context of oxygen utilization by this anaerobic organism is discussed.

Direct selection of IS903 transposon insertions by use of a broad-host-range vector: isolation of catalase-deficient mutants of Actinobacillus actinomycetemcomitans

Transposon mutagenesis in bacteria generally requires efficient delivery of a transposon suicide vector to allow the selection of relatively infrequent transposition events. We have developed an IS903-based transposon mutagenesis system for diverse gram-negative bacteria that is not limited by transfer efficiency. The transposon, IS903phikan, carries a cryptic kan gene, which can be expressed only after successful transposition. This allows the stable introduction of the transposon delivery vector into the host. Generation of insertion mutants is then limited only by the frequency of transposition. IS903phikan was placed on an IncQ plasmid vector with the transposase gene located outside the transposon and expressed from isopropyl-beta-D-thiogalactopyranoside (IPTG)-inducible promoters. After transposase induction, IS903phikan insertion mutants were readily selected in Escherichia coli by their resistance to kanamycin. We used IS903phikan to isolate three catalase-deficient mutants of the periodontal pathogen Actinobacillus actinomycetemcomitans from a library of random insertions. The mutants display increased sensitivity to hydrogen peroxide, and all have IS903phikan insertions within an open reading frame whose predicted product is closely related to other bacterial catalases. Nucleotide sequence analysis of the catalase gene (designated katA) and flanking intergenic regions also revealed several occurrences of an 11-bp sequence that is closely related to the core DNA uptake signal sequence for natural transformation of Haemophilus influenzae. Our results demonstrate the utility of the IS903phikan mutagenesis system for the study of A. actinomycetemcomitans. Because IS903phikan is carried on a mobilizable, broad-host-range IncQ plasmid, this system is potentially useful in a variety of bacterial species.

Decreased intracellular superoxide levels activate Sindbis virus-induced apoptosis

Infection of many cultured cell types with Sindbis virus (SV), an alphavirus, triggers apoptosis through a commonly utilized caspase activation pathway. However, the upstream signals by which SV activates downstream apoptotic effectors, including caspases, remain unclear. Here we report that in AT-3 prostate carcinoma cells, SV infection decreases superoxide (O-2) levels within minutes of infection as monitored by an aconitase activity assay. This SV-induced decrease in O-2 levels appears to activate or modulate cell death, as a recombinant SV expressing the O-2 scavenging enzyme, copper/zinc superoxide dismutase (SOD), potentiates SV-induced apoptosis. A recombinant SV expressing a mutant form of SOD, which has reduced SOD activity, has no effect. The potentiation of SV-induced apoptosis by wild type SOD is because of its ability to scavenge intracellular O-2 rather than its ability to promote the generation of hydrogen peroxide. Pyruvate, a peroxide scavenger, does not affect the ability of wild type SOD to potentiate cell death; and increasing the intracellular catalase activity via a recombinant SV vector has no effect on SV-induced apoptosis. Moreover, increasing intracellular O-2 by treatment of 3T3 cells with paraquat protects them from SV-induced death. Altogether, our results suggest that SV may activate apoptosis by reducing intracellular superoxide levels and define a novel redox signaling pathway by which viruses can trigger cell death.

Antiseptics and disinfectants: activity, action, and resistance

Antiseptics and disinfectants are extensively used in hospitals and other health care settings for a variety of topical and hard-surface applications. A wide variety of active chemical agents (biocides) are found in these products, many of which have been used for hundreds of years, including alcohols, phenols, iodine, and chlorine. Most of these active agents demonstrate broad-spectrum antimicrobial activity; however, little is known about the mode of action of these agents in comparison to antibiotics. This review considers what is known about the mode of action and spectrum of activity of antiseptics and disinfectants. The widespread use of these products has prompted some speculation on the development of microbial resistance, in particular whether antibiotic resistance is induced by antiseptics or disinfectants. Known mechanisms of microbial resistance (both intrinsic and acquired) to biocides are reviewed, with emphasis on the clinical implications of these reports.

Characterization of a facultatively psychrophilic bacterium, vibrio rumoiensis sp. nov., that exhibits high catalase activity

A novel facultatively psychrophilic bacterium, strain S-1, which exhibits extraordinarily high catalase activity was isolated from the drain pool of a fish product processing plant that uses H2O2 as a bleaching and microbicidal agent. The catalase activity of the isolate was 1 or 2 orders of magnitude higher than those of Corynebacterium glutamicum, Staphylococcus aureus, Pseudomonas fluorescens, and five other species tested in this study. The strain seemed to possess only one kind of catalase, according to the results of polyacrylamide gel electrophoresis of the cell extract. The optimum temperature for catalase activity was about 30 degreesC, which was about 20 degreesC lower than that for bovine catalase activity. Electron microscopic observation revealed that the surface of the microorganism was covered by blebs. Although the isolate was nonflagellated, its taxonomic position on the basis of physiological and biochemical characteristics and analysis of 16S rRNA sequence and DNA-DNA relatedness data indicated that strain S-1 is a new species belonging to the genus Vibrio. Accordingly, we propose the name Vibrio rumoiensis. The type strain is S-1 (FERM P-14531).

A mechanism of resistance to hydrogen peroxide in Vibrio rumoiensis S-1

A possible mechanism of resistance to hydrogen peroxide (H2O2) in Vibrio rumoiensis, isolated from the H2O2-rich drain pool of a fish processing plant, was examined. When V. rumoiensis cells were inoculated into medium containing either 5 mM or no H2O2, they grew in similar manners. A spontaneous mutant strain, S-4, derived from V. rumoiensis and lacking catalase activity did not grow at all in the presence of 5 mM H2O2. These results suggest that catalase is inevitably involved in the resistance and survival of V. rumoiensis in the presence of H2O2. Catalase activity was constitutively present in V. rumoiensis cells grown in the absence of H2O2, and its occurrence was dependent on the age of the cells, a characteristic which is observed for the HP II-type catalase of Escherichia coli. The presence of the HP II-type catalase in V. rumoiensis cells was evidenced by partial sequencing of the gene encoding the HP II-type catalase from this organism. A notable difference between V. rumoiensis and E. coli is that catalase is accumulated at very high levels ( approximately 2% of the total soluble proteins) in V. rumoiensis, in contrast to the case for E. coli. When V. rumoiensis cells which had been exposed to 5 mM H2O2 were centrifuged, most intracellular proteins, including catalase, were recovered in the medium. On the other hand, when V. rumoiensis cells were grown on plates containing various concentrations of H2O2, individual cells had a colony-forming ability inferior to those of E. coli, Bacillus subtilis, and Vibrio parahaemolyticus. Thus, it is suggested that when V. rumoiensis cells are exposed to high concentrations of H2O2, most cells will immediately be broken by H2O2. In addition, the cells which have had little or no damage will start to grow in a medium where almost all H2O2 has been decomposed by the catalase released from broken cells.

The periplasmic, group III catalase of Vibrio fischeri is required for normal symbiotic competence and is induced both by oxidative stress and by approach to stationary phase

The catalase gene, katA, of the sepiolid squid symbiont Vibrio fischeri has been cloned and sequenced. The predicted amino acid sequence of KatA has a high degree of similarity to the recently defined group III catalases, including those found in Haemophilus influenzae, Bacteroides fragilis, and Proteus mirabilis. Upstream of the predicted start codon of katA is a sequence that closely matches the consensus sequence for promoters regulated in Escherichia coli by the alternative sigma factor encoded by rpoS. Further, the level of expression of the cloned katA gene in an E. coli rpoS mutant is much lower than in wild-type E. coli. Catalase activity is induced three- to fourfold both as growing V. fischeri cells approach stationary phase and upon the addition of a small amount of hydrogen peroxide during logarithmic growth. The catalase activity was localized in the periplasm of wild-type V. fischeri cells, where its role could be to detoxify hydrogen peroxide coming from the external environment. No significant catalase activity could be detected in a katA null mutant strain, demonstrating that KatA is the predominately expressed catalase in V. fischeri and indicating that V. fischeri carries only a single catalase gene. The catalase mutant was defective in its ability to competitively colonize the light organs of juvenile squids in coinoculation experiments with the parent strain, suggesting that the catalase enzyme plays an important role in the symbiosis between V. fischeri and its squid host.

Regulation of Bacteriodes fragilis katB mRNA by oxidative stress and carbon limitation

Regulation of the katB catalase gene in the anaerobic bacterium Bacteroides fragilis was studied. Northern blot hybridization analyses revealed that katB was transcribed as an approximately 1.6-kb monocistronic mRNA. The levels of katB mRNA increased > 15-fold when anaerobic, mid-logarithmic-phase cultures were exposed to O2, O2 with paraquat, or hydrogen peroxide. Under anaerobic conditions, the low levels of katB mRNA increased in a growth-dependent manner, reaching maximum expression at late logarithmic or early stationary phase, followed by a decrease in stationary phase. Under anaerobic conditions, the expression of katB mRNA was strongly repressed by glucose and to a lesser extent by xylose. However, glucose repression was completely abolished upon exposure to oxygen. The nonfermentable carbon sources fumarate, succinate, acetate, and pyruvate did not significantly affect expression. Phosphate, nitrogen, and hemin limitation did not affect the expression of katB mRNA, suggesting that the nutritional control of katB expression is restricted to carbon and energy sources and not other forms of nutrient limitation. Primer extension analysis revealed that during both oxidative stress and carbon or energy limitation, katB utilized the same promoter region but transcription initiation occurred at two different nucleotides separated by 3 or 4 bases. Interestingly, a 6-bp inverted repeat sequence present in the katB regulatory region was also observed upstream of the B. fragilis superoxide dismutase gene sod. It is possible that this is a recognition site for a DNA binding protein involved in the regulation of oxidative stress genes in this organism.

Cloning and characterization of the katA gene of Rhizobium meliloti encoding a hydrogen peroxide-inducible catalase

To investigate the involvement of bacterial catalases of the symbiotic gram-negative bacterium Rhizobium meliloti in the development of Medicago-Rhizobium functional nodules, we cloned a putative kat gene by screening a cosmid library with a catalase-specific DNA probe amplified by PCR from the R. meliloti genome. Nucleotide sequence analysis of a 1.8-kb DNA fragment revealed an open reading frame, called katA, encoding a peptide of 562 amino acid residues with a calculated molecular mass of 62.9 kDa. The predicted amino acid sequence showed a high homology with the primary structure of monofunctional catalases from eucaryotes and procaryotes. The katA gene was localized on the chromosome, and the katA gene product was essentially found in the periplasmic space. A katA::Tn5 mutant was obtained and showed a drastic sensitivity to hydrogen peroxide, indicating an essential protective role of KatA. However, neither Nod nor Fix phenotypes were impaired in the mutant, suggesting that KatA is not essential for nodulation and establishment of nitrogen fixation. Exposure to a sublethal concentration of H2O2 enhanced KatA activity (100-fold) and also increased survival to subsequent H2O2 exposure at higher concentrations. No protection is observed in katA::Tn5, indicating that KatA is the major component of an adaptive response.

Cloning and genetic characterization of Helicobacter pylori catalase and construction of a catalase-deficient mutant strain

The N-terminal sequence of a protein, originally described as an adhesin of Helicobacter pylori, was used in an oligonucleotide-based screening procedure of an H. pylori plasmid library in Escherichia coli. Five independent plasmid clones were isolated, all mapping to the same chromosomal region and encoding the H. pylori catalase. The gene, designated katA, comprises 1,518 nucleotides and encodes a putative protein of 505 amino acids with a predicted Mr of 58,599. A second open reading frame, orf2, encoding a putative 32,715-Da protein of unknown function, follows katA. The transcriptional start site of katA mRNA was determined, but no typical consensus promoter sequence was present. A potential binding site for the Fur protein is located upstream of katA. When introduced into the catalase-deficient E. coli double-mutant UM255, the cloned gene readily complemented E. coli for catalase activity. H. pylori KatA is highly homologous to catalases in both prokaryotes and eukaryotes, with the highest homology being shown to Bordetella pertussis (64.9%), Bacteroides fragilis (59.8%), and Haemophilus influenzae (57.9%) catalases. Transposon insertion mutants were generated in three independent H. pylori strains by TnMax5-mediated transposon shuttle mutagenesis. In contrast to the wild-type strains, no significant catalase-specific enzymatic activity could be detected in the mutant strains, consistent with the fact that no additional katA-homologous gene copies were found in the H. pylori chromosome. No significant difference between wild-type and mutant strains for binding to epithelial cells was apparent, suggesting that KatA is not involved in H. pylori adhesion. The cloning and genetic characterization of katA are essential steps for further investigation of the role of catalase in the defense of H. pylori against oxygen-dependent killing mechanisms by polymorphonuclear granulocytes, a process not well understood for this chronically persisting pathogen.

Regulation of the oxidative stress protective enzymes, catalase and superoxide dismutase in Xanthomonas--a review

Xanthomonas showed atypical regulation of catalase (Kat) and superoxide dismutase with respect to growth phase and response to various inducers. The highest levels of both enzymes were detected during early log phase of growth and declined as growth continued. This was in contrast to resistance levels to superoxides, H2O2 and organic peroxides, which reached maximum levels during stationary phase. Xanthomonas catalase was induced over six fold by superoxide generators and methyl methane sulfonate but weakly by H2O2. The regulation pattern of these enzymes could be important during plant/microbe interactions. To facilitate elucidation of Xanthomonas kat gene regulation, highly conserved regions of monofuctional Kat amino acid sequences were used to synthesize oligodeoxyribonucleotide primers for use in PCR reactions with Xanthomonas genomic DNA as templates. The Xanthomonas-specific PCR kat probe was used to isolate a functional kat from Xanthomonas campestris pv. phaseoli.

Lack of expression of the global regulator OxyR in Haemophilus influenzae has a profound effect on growth phenotype

A pBR322-based library of chromosomal DNA from the nontypeable Haemophilus influenzae TN106 was screened for the expression of transferrin-binding activity in Escherichia coli. A recombinant clone expressing transferrin-binding activity contained a 3.7-kb fragment of nontypeable H. influenzae DNA. Nucleotide sequence analysis of this insert revealed the presence of two complete open reading frames encoding proteins of approximately 26 and 34 kDa. Mini-Tn10kan transposon mutagenesis at different sites within the open reading frame encoding the 34-kDa protein resulted in the abolition of transferrin-binding activity in the recombinant E. coli clone. The deduced amino acid sequence of the 34-kDa protein had 70% identity with the OxyR protein of E. coli; this latter macromolecule is a member of the LysR family of transcriptional activators. When a mutated H. influenzae oxyR gene was introduced into the chromosome of the wild-type H. influenzae strain by allelic exchange, the resulting oxyR mutant still exhibited wild-type levels of transferrin-binding activity but was unable to grow on media containing the heme precursor protoporphyrin IX (PPIX) in place of heme. This mutant also exhibited reduced growth around disks impregnated with heme sources. Supplementation of the PPIX-based growth media with catalase or sodium pyruvate resulted in normal growth of the H. influenzae oxyR mutant. Provision of the wild-type H. influenzae oxyR gene in trans also permitted the growth of this mutant on a PPIX-based medium. Exogenously supplied catalase restored the growth of this mutant with heme sources to nearly wild-type levels. These results indicate that expression of a wild-type OxyR protein by H. influenzae is essential to allow this organism to protect itself against oxidative stresses in vitro.

Cloning and characterization of the catalase gene of Neisseria gonorrhoeae: use of the gonococcus as a host organism for recombinant DNA

The structural gene for the catalase of Neisseria gonorrhoeae was cloned into a Kat- strain of that organism by using a recombinant vector derived from one of the beta-lactamase-specifying plasmids found in that organism. The kat gene was then successfully subcloned into both pUC8 and pGB2, transformed into Escherichia coli, and shown to complement the E. coli katE mutants UM2 and UMRl. The gene was subsequently mutagenized and returned to the gonococcus to generate a Kat- strain that was phenotypically identical to the strain originally used to clone the gene. The sequence of the gene and the derived amino acid sequence showed that the gonococcal kat gene closely resembles the hktE gene of Haemophilus influenzae. The sequence of the promoter region of the gonococcal kat gene is unusual and may explain the extremely high, loosely regulated expression of the gene.

Heterologous growth phase- and temperature-dependent expression and H2O2 toxicity protection of a superoxide-inducible monofunctional catalase gene from Xanthomonas oryzae pv. oryzae

Catalase is an important protective enzyme against H2O2 toxicity. Here, we report the characterization of a Xanthomonas oryzae pv. oryzae catalase gene (katX). The gene was localized and its nucleotide sequence was determined. The gene codes for a 77-kDa polypeptide. The deduced katX amino acid sequence shares regions of high identity with other monofunctional catalases in a range of organisms from bacteria to eukaryotes. The transcriptional regulation of katX was atypical of bacterial monofunctional kat genes. Northern (RNA) analysis showed that katX transcription was highly induced by treatments with low concentrations of menadione, a superoxide generator, and methyl methanesulfonate, a mutagen. It was only weakly induced by H2O2. Unlike in other bacteria, a high level of catalase in Xanthomonas spp. provided protection from the growth-inhibitory and killing effects of H2O2 but not from those of organic peroxides and superoxide generators. Unexpectedly, heterologous expression of katX in Escherichia coli was both growth phase and temperature dependent. Catalase activity in E. coli kat mutants harboring katX on an expression vector was detectable only when the cells entered the stationary phase of growth and at 28 degrees C. The patterns of transcription regulation, heterologous expression, and physiological function of katX are different from previously studied bacterial kat genes.

Cloning, sequencing and disruption of a bromoperoxidase-catalase gene in Streptomyces venezuelae: evidence that it is not required for chlorination in chloramphenicol biosynthesis

Genomic DNA libraries of Streptomyces venezuelae ISP5230 and of a mutant blocked at the chlorination step of chloramphenicol biosynthesis were probed by hybridization with a synthetic oligonucleotide corresponding to the N-terminal amino acid sequence of a bromoperoxidase-catalase purified from the wild-type strain. Hybridizing fragments obtained from the two strains were cloned and sequenced. Analysis of the nucleotide sequences demonstrated that the fragments contained the same 1449 bp open reading frame with no differences in nucleotide sequence. The deduced polypeptide encoded 483 amino acids with a calculated M(r) of 54,200; the N-terminal sequence was identical to that of the bromoperoxidase-catalase purified from wild-type S. venezuelae. Comparison of the amino acid sequence predicted for the cloned bromoperoxidase-catalase gene (bca) with database protein sequences showed a significant similarity to a group of prokaryotic and eukaryotic catalases, but none to other peroxidases or haloperoxidases. Replacement of the bca gene in the wild-type strain of S. venezuelae with a copy disrupted by insertion of a DNA fragment encoding apramycin resistance did not prevent chloramphenicol production. The results suggest that the role of the enzyme in S. venezuelae is related to its activity as a catalase rather than as a halogenating agent.

Role of Escherichia coli rpoS and associated genes in defense against oxidative damage

The first phenotype described for mutations in the Escherichia coli rpoS gene was hypersensitivity to near-ultraviolet radiation and to its oxidative photoproduct, hydrogen peroxide. Initially named nur, this gene is now known to code for a sigma factor, and has acquired new names such as katF and rpoS. The role of its protein product (sigma-38) is to regulate a battery of genes as cells enter and rest in stationary phase. Some of the gene products are involved in protection against oxidants (e.g., catalases) and repair of oxidative damage (e.g., exonuclease III). Sigma-38 may also modulate transcription of certain growth phase genes, including hydroperoxidase I and glutathione reductase. Sigma-38 activity is regulated at transcriptional, translational, and protein stabilization levels. This review describes the complex mechanisms whereby sigma-38 controls various genes, the interaction of sigma-38 with other regulators, and a possible role of sigma-38 in bacterial virulence.

Cloning, characterization and phenotypic expression in Escherichia coli of catF, which encodes the catalytic subunit of catalase isozyme CatF of Pseudomonas syringae

The phytophathogenic, gram-negative bacterium Pseudomonas syringae pv. syringae 61 contains three isozymes of catalase (EC 1.11.1.6), which have been proposed to play a role in the bacterium's responses to various environmental stresses. To study the role of individual isozymes, the gene coding for the catalytic subunit of one catalase isozyme was cloned from a cosmid library hosted in Escherichia coli DH5 alpha by using a designed catalase-specific DNA probe for the screening. One out of four clones with a catalase-positive genotype was subcloned and a pUC19-based 2.7 x 10(3)-base (2.7-kb) insert subclone, pMK3E5, was used to transform catalase-deficient E. coli strain UM255 (HPI-, HPII-). The transformants contained a single isozyme of catalase that had electrophoretic and enzymic properties similar to catalase isozyme CatF from P. syringae pv. syringae 61. Analysis of the sequenced 2.7-kb insert DNA revealed six putative open-reading frames (ORF). The 1542-base-pair DNA sequence of ORF2, called catF, encodes a peptide of 513 amino acid residues with a calculated molecular mass of 66.6 kDa. The amino acid sequence deduced from catF had homology to the primary structure of true catalases from mammals, plants, yeasts and bacteria. The activity of the recombinant catalase was inhibited by 3-amino-1,2,4-triazole and azide and stimulated by chloramphenicol. The N terminus contained a signal sequence of 26 amino acids necessary for secretion into the periplasm, a so-far unique property of Pseudomonas catalases.

A catalase from Streptomyces coelicolor A3(2)

Catalase was purified from the Gram-positive bacterium Streptomyces coelicolor A3(2) in a three-step purification procedure comprising (NH4)2SO4 fractionation, Phenyl-Sepharose chromatography and Mono Q chromatography. The purification of catalase, as judged by the final specific activity of 110,000 U mg-1, was 250-fold with a 35% yield. The native protein was a homotetramer with a subunit M(r) 55,000. N-terminal and internal peptide sequence analyses showed that there was a high degree of sequence similarity between the S. coelicolor catalase and other microbial and mammalian catalases. Southern blot analysis indicated that there was a single catalase gene in S. coelicolor. The specific activity of catalase throughout the growth of batch cultures was investigated and elevated catalase activity was found in stationary-phase cells.

Biochemical and genetic analyses of a catalase from the anaerobic bacterium Bacteroides fragilis

A single catalase enzyme was produced by the anaerobic bacterium Bacteroides fragilis when cultures at late log phase were shifted to aerobic conditions. In anaerobic conditions, catalase activity was detected in stationary-phase cultures, indicating that not only oxygen exposure but also starvation may affect the production of this antioxidant enzyme. The purified enzyme showed a peroxidatic activity when pyrogallol was used as an electron donor. It is a hemoprotein containing one heme molecule per holomer and has an estimated molecular weight of 124,000 to 130,000. The catalase gene was cloned by screening a B. fragilis library for complementation of catalase activity in an Escherichia coli catalase mutant (katE katG) strain. The cloned gene, designated katB, encoded a catalase enzyme with electrophoretic mobility identical to that of the purified protein from the B. fragilis parental strain. The nucleotide sequence of katB revealed a 1,461-bp open reading frame for a protein with 486 amino acids and a predicted molecular weight of 55,905. This result was very close to the 60,000 Da determined by denaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified catalase and indicates that the native enzyme is composed of two identical subunits. The N-terminal amino acid sequence of the purified catalase obtained by Edman degradation confirmed that it is a product of katB. The amino acid sequence of KatB showed high similarity to Haemophilus influenzae HktE (71.6% identity, 66% nucleotide identity), as well as to gram-positive bacterial and mammalian catalases. No similarities to bacterial catalase-peroxidase-type enzymes were found. The active-site residues, proximal and distal hemebinding ligands, and NADPH-binding residues of the bovine liver catalase-type enzyme were highly conserved in B. fragilis KatB.

Molecular characterization of katA from Campylobacter jejuni and generation of a catalase-deficient mutant of Campylobacter coli by interspecific allelic exchange

A gene encoding catalase (hydrogen-peroxide:hydrogen-peroxide oxidoreductase; EC 1.11.1.6) from Campylobacter jejuni was cloned by functional complementation of a catalase-deficient mutant of Escherichia coli. The catalase structural gene, designated katA, was assigned by subcloning and its nucleotide sequence determined. The deduced protein product of 508 amino acids, which had a calculated molecular mass of 58,346 Da, was found to be structurally and enzymically similar to hydrogen-peroxidases from other bacterial species. The region of DNA containing the structural catalase gene was disrupted by insertion of a tetracycline-resistance marker and the modified sequence then introduced into a strain of Campylobacter coli via natural transformation. Genetic and enzymic analyses of a tetracycline-resistant C. coli transformant confirmed that catalase-deficient mutants had arisen via interspecific allelic exchange. Compared to the isogenic parental strain the mutant was more sensitive to killing by H2O2.

Unusual Growth Phase and Oxygen Tension Regulation of Oxidative Stress Protection Enzymes, Catalase and Superoxide Dismutase, in the Phytopathogen Xanthomonas oryzae pv. oryzae

The enzymes catalase and superoxide dismutase play major roles in protecting phytopathogenic bacteria from oxidative stress. In Xanthomonas species, these enzymes are regulated by both growth phase and oxygen tension. The highest enzyme levels were detected within 1 h of growth. Continued growth resulted in a decline of both enzyme activities. High oxygen tension was an inducing signal for both enzyme activities. An 80,000-Da monofunctional catalase and a manganese superoxide dismutase were the major forms of the enzymes detected at different stages of growth. The unusual regulatory patterns are common among several Xanthomonas strains tested and may be advantageous to Xanthomonas species during the initial stage of plant-microorganism interactions.