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M A Mandrand

Publications and source records attributed to M A Mandrand.

5 recordsLinked to original sources
PubMed1994

Antagonistic effect of nickel on the fermentative growth of Escherichia coli K-12 and comparison of nickel and cobalt toxicity on the aerobic and anaerobic growth.

The facultative anaerobic enterobacterium Escherichia coli requires the activity of nickel-containing hydrogenase for its anaerobic growth. Deficiency of the specific nickel transport system led to a hydrogenase-minus phenotype and slowed down the fermentative growth in the nik mutant. Addition of 300 microM nickel to the growth medium could restore the hydrogenase activity. This restoration resulted in the recovery of anaerobic growth. A further increase of nickel concentration inhibited growth. Thus nickel shows an antagonistic effect on the anaerobic growth of E. coli. To study the mechanism of nickel toxicity, two classes of nickel-resistant mutants were isolated. The nkr mutant was obtained by selecting colonies grown on nickel-containing minimal plate. It acquired simultaneously the resistance to cobalt. A nonspecific magnesium transport mutant corA was isolated on cobalt-containing plate. The corA mutant was also resistant to nickel. When analyzing the influence of nickel and cobalt on the bacterial growth, we obtained two interesting observations. First, anaerobic growth was less sensitive than aerobic growth to cobalt toxicity. In contrast, nickel toxicity did not vary from the growth conditions. Second, cobalt seems to abolish the growth, while nickel appears to slow down the growth rate under the condition used.

Aerobiosis↗
PubMed1993

Microbial hydrogenases: primary structure, classification, signatures and phylogeny.

Thirty sequenced microbial hydrogenases are classified into six classes according to sequence homologies, metal content and physiological function. The first class contains nine H2-uptake membrane-bound NiFe-hydrogenases from eight aerobic, facultative anaerobic and anaerobic bacteria. The second comprises four periplasmic and two membrane-bound H2-uptake NiFe(Se)-hydrogenases from sulphate-reducing bacteria. The third consists of four periplasmic Fe-hydrogenases from strict anaerobic bacteria. The fourth contains eight methyl-viologen- (MV), factor F420- (F420) or NAD-reducing soluble hydrogenases from methanobacteria and Alcaligenes eutrophusH16. The fifth is the H2-producing labile hydrogenase isoenzyme 3 of Escherichia coli. The sixth class contains two soluble tritium-exchange hydrogenases of cyanobacteria. The results of sequence comparison reveal that the 30 hydrogenases have evolved from at least three different ancestors. While those of class I, II, IV and V hydrogenases are homologous, i.e. sharing the same evolutionary origin, both class III and VI hydrogenases are neither related to each other nor to the other classes. Sequence comparison scores, hierarchical cluster structures and phylogenetic trees show that class II falls into two distinct clusters composed of NiFe- and NiFeSe-hydrogenases, respectively. These results also reveal that class IV comprises three distinct clusters: MV-reducing, F420-reducing and NAD-reducing hydrogenases. Specific signatures of the six classes of hydrogenases as well as some subclusters have been detected. Analyses of motif compositions indicate that all hydrogenases, except those of class VI, must contain some common motifs probably participating in the formation of hydrogen activation domains and electron transfer domains. The regions of hydrogen activation domains are highly conserved and can be divided into two categories. One corresponds to the 'nickel active center' of NiFe(Se)-hydrogenases. It consists of two possible specific nickel-binding motifs, RxCGxCxxxH and DPCxxCxxH, located at the N- and C-termini of so-called large subunits in the dimeric hydrogenases, respectively. The other is the H-cluster of the Fe-hydrogenases. It might comprise three motifs on the C-terminal half of the large subunits. However, the motifs corresponding to the putative electron transfer domains, as well as their polypeptides chains, are poorly or even not at all conserved. They are present essentially on the small subunits in NiFe-hydrogenases. Some of these motifs resemble the typical ferredoxin-like Fe-S cluster binding site.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1992

A second phenazine methosulphate-linked formate dehydrogenase isoenzyme in Escherichia coli.

A biochemical and immunological study has revealed a new formate dehydrogenase isoenzyme in Escherichia coli. The enzyme is an isoenzyme of the respiratory formate dehydrogenase (FDH-N) which forms part of the formate to nitrate respiratory pathway found in the organisms when it is grown anaerobically in the presence of nitrate. The new enzyme, termed FDH-Z, cross reacts with antibodies raised to FDH-N and possesses a similar polypeptide composition to FDH-N. FDH-Z catalyses the phenazine methosulphate-linked formate dehydrogenase activity present in the aerobically-grown bacterium. FDH-Z and FDH-N exhibit distinct regulation. Like formate dehydrogenase N, formate dehydrogenase Z is a membrane-bound molybdoenzyme. With nitrate reductase it can catalyse electron transfer between formate and nitrate. Quinones are required for the physiological electron transfer to nitrate. It seems likely that like FDH-N, FDH-Z functions physiologically as a formate: quinone oxidoreductase.

Electron Transport↗
PubMed1990

Identification and expression of the Escherichia coli fdhD and fdhE genes, which are involved in the formation of respiratory formate dehydrogenase.

The two closely linked fdhD and fdhE genes of Escherichia coli are required for the formation of active membrane-bound phenazine methosulfate-linked formate dehydrogenase (FDH-PMS). Both genes were isolated from a cosmid library. Restriction endonuclease analysis associated with Mu dII1734 insertion mutagenesis indicated that the two genes were separated by at least 4 kilobases and transcribed in opposite orientations. Initial experiments indicate that the region between the two genes seems not to be essential to FDH-PMS activity. fdhD and fdhE were expressed either in maxicells or from the T7 promoter-polymerase system. They were shown to encode proteins with approximate Mr 30,500 and 32,000, respectively. Both proteins appeared in the soluble fraction and were not recognized by an FDH-PMS-specific antiserum. Therefore, neither fdhD nor fdhE plays a structural role in the formation of FDH-PMS. Expression of a phi(fdhD-lacZ) operon fusion was decreased about threefold by aerobiosis but was indifferent to other effectors tested. It was unaffected by pfl, chlA, selA, and fnr mutations. Expression of a phi(fdhE-lacZ) operon fusion was slightly induced by nitrate. This induction, requiring the presence of functional chl and fnr alleles, was mediated via nitrate metabolism. Transcription of phi(fdhE-lacZ) fusion was fully dependent on wild-type sel alleles. This might suggest the participation of fdhE in the synthesis of the selenopolypeptide of FDH-PMS.

Cloning, Molecular↗