Increase in the Culturable Cell Number of Escherichia coli during Recovery from Saline Stress: Possible Implication for Resuscitation from the VBNC State

The change in colony-forming units (CFUs) in saline-stressed Escherichia coli cultures was examined. Exposure of E. coli cells to high saline stress decreased the number of CFUs significantly. When the culture was relieved from the stressful condition, the number of CFUs returned within 2 hr to the same level as before the stress. This recovery in the number of CFUs seemed to be independent of DNA synthesis and cell division, because the same phenomenon was also observed in the presence of nalidixic acid. However, the total cell number enumerated by microscopy was the same before and after relief from saline stress. This phenomenon was considered to be the result of the resuscitation of cells that had been in the VBNC state during saline stress. Our method, in which we examined CFU recovery in the presence of a DNA synthesis inhibitor, might be useful for further VBNC study.

Role of inorganic polyphosphate in promoting ribosomal protein degradation by the Lon protease in E. coli

Inorganic polyphosphate (polyP), a polymer of hundreds of phosphate (Pi) residues, accumulates in Escherichia coli in response to stresses, including amino acid starvation. Here we show that the adenosine 5'-triphosphate-dependent protease Lon formed a complex with polyP and degraded most of the ribosomal proteins, including S2, L9, and L13. Purified S2 also bound to polyP and formed a complex with Lon in the presence of polyP. Thus, polyP may promote ribosomal protein degradation by the Lon protease, thereby supplying the amino acids needed to respond to starvation.

Peroxisome proliferators activate cytochrome P450 genes in an alkane-assimilating yeast, Candida maltosa

Candida maltosa can assimilate n-alkane as a sole carbon source and cytochromes P450ALK (P450ALK) are critical for the first oxidation step. Four major P450ALKs that are encoded by genes ALK1, ALK2, ALK3 and ALK5 are induced by n-alkane and repressed by glucose at the transcriptional level. In the present work, we found that all these four genes but ALK5 are transcriptionally activated in response to a peroxisome proliferator, clofibrate. This is the first report on the peroxisome proliferator responsive gene expression in lower eucaryotes.

Evidence that the expression of the gene for NADPH-cytochrome P-450 reductase is n-alkane-inducible in Candida maltosa

A gene coding for NADPH-cytochrome P-450 reductase of an n-alkane-assimilating yeast, Candida maltosa, was isolated and sequenced. Northern analysis and assay of the expression of the reporter gene under the control of the promoter of this gene showed that the transcriptional level was induced 4 to 8-fold in cells grown on n-alkane relative to cells grown on glucose.

Cloning and sequencing of a 2,5-dichloro-2,5-cyclohexadiene-1,4-diol dehydrogenase gene involved in the degradation of gamma-hexachlorocyclohexane in Pseudomonas paucimobilis

In Pseudomonas paucimobilis UT26, gamma-hexachlorocyclohexane (gamma-HCH) is converted to 2,5-dichloro-2,5-cyclohexadiene-1,4-diol (2,5-DDOL), which is then metabolized to 2,5-dichlorohydroquinone. Here, we isolated from the genomic library of UT26 two genes which expressed 2,5-DDOL dehydrogenase activity when they were transformed into P. putida and Escherichia coli. Both gene products had an apparent molecular size of 28 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The first gene, named linC, located separately from the two genes (linA and linB) which we had already cloned as genes involved in the gamma-HCH degradation. The other, named linX, located about 1 kb upstream of the linA gene encoding gamma-HCH dehydrochlorinase. A gamma-HCH degradation-negative mutant, named UT72, which lacked the whole linC gene but had the intact linX gene was isolated. The linC gene given in a plasmid could complement UT72. These results strongly suggest that the linC gene but not the linX gene is essential for the assimilation of gamma-HCH in UT26. Deduced amino acid sequences of LinC and LinX show homology to those of members of the short-chain alcohol dehydrogenase family.

Cloning and sequencing of a dehalogenase gene encoding an enzyme with hydrolase activity involved in the degradation of gamma-hexachlorocyclohexane in Pseudomonas paucimobilis

In Pseudomonas paucimobilis UT26, gamma-hexachlorocyclohexane (gamma-HCH) is converted by two steps of dehydrochlorination to a chemically unstable intermediate, 1,3,4,6-tetrachloro-1,4-cyclohexadiene (1,4-TCDN), which is then metabolized to 2,5-dichloro-2,5-cyclohexadiene-1,4-diol (2,5-DDOL) by two steps of hydrolytic dehalogenation via the chemically unstable intermediate 2,4,5-trichloro-2,5-cyclohexadiene-1-ol (2,4,5-DNOL). To clone a gene encoding the enzyme responsible for the conversion of the chemically unstable intermediates 1,4-TCDN and 2,4,5-DNOL, a genomic library of P. paucimobilis UT26 was constructed in Pseudomonas putida PpY101LA into which the linA gene had been introduced by Tn5. An 8-kb BglII fragment from one of the cosmid clones, which could convert gamma-HCH to 2,5-DDOL, was subcloned, and subsequent deletion analyses revealed that a ca. 1.1-kb region was responsible for the activity. Nucleotide sequence analysis revealed an open reading frame (designated the linB gene) of 885 bp within the region. The deduced amino acid sequence of LinB showed significant similarity to hydrolytic dehalogenase, DhlA (D. B. Janssen, F. Pries, J. van der Ploeg, B. Kazemier, P. Terpstra, and B. Witholt, J. Bacteriol. 171:6791-6799, 1989). The protein product of the linB gene was 32 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Not only 1-chlorobutane but also 1-chlorodecane (C10) and 2-chlorobutane, which are poor substrates for other dehalogenases, were good substrates for LinB, suggesting that LinB may be a member of haloalkane dehalogenases with broad-range specificity for substrates.

Pure alexia in Japanese and agraphia without alexia in kanji. The ability dissociation between reading and writing in kanji vs kana

A 60-year-old right-handed Japanese man with infarction of the left occipital lobe and inferior temporal gyrus initially showed pure alexia in kana and kanji. Later, though pure alexia in kana persisted, his kanji reading improved markedly, but with little improvement of kanji writing. We speculate that different pathways are involved in kanji reading and writing. Wernicke's area and its surrounding left middle temporal lobe might play the most important role for kanji reading when visual information is transmitted by any pathway. The pathway from Wernicke's area to the left occipital lobe via the middle and inferior temporal pathway may be indispensable for kanji writing. We postulate "agraphia without alexia in kanji" due to left inferior temporal subcortical damage.