- Volume 144, Issue 10, 1998
Volume 144, Issue 10, 1998
- Pathogenicity And Medical Microbiology
-
-
-
The two-component hybrid kinase regulator CaNIKl of Candida albicans
More LessSUMMARY: Using degenerate primers of highly conserved regions of two-component response regulators for PCR amplification, a two-component response regulator was cloned from Candida albicans that is homologous to nik-l+ of Neurospora crassa. This two-component hybrid kinase, CaNIKl, also shows features of bacterial two-component response regulators, including a putative unorthodox second histidine kinase motif at the carboxy-terminal end. CaNIKl was expressed at low levels in both the white and opaque switch phenotypes and in the bud and hyphal growth forms of C. albicans strain WO-1, but in both developmental programmes, the level of transcript was modulated (levels were higher in opaque cells and in hyphae). Partial deletion of both CaNIKl alleles, by which the histidine autokinase- and ATP-binding domains were removed, did not inhibit either high-frequency phenotypic switching or the bud-hypha transition in high salt concentrations, but in both cases the efficiency of the developmental process was reduced.
-
-
- Physiology And Growth
-
-
-
Pleiotropic effects of the opil regulatory mutation of yeast: its effects on growth and on phospholipid and inositol metabolism
More LessSUMMARY: Key factors which impact on the biosynthesis and subsequent fate of the phospholipid precursor inositol were studied as a function of growth phase in the yeast Sacchammyces cerevisiae. Both wild-type and strains disrupted for the OPI7 gene, the principal negative regulator of the phospholipid biosynthetic genes, were examined. Overexpression of the IN07 gene and overproduction of both inositol and the major inositol-containing phospholipid, phosphatidylinositol. varied as a function of growth phase. In Opi7 cells, IN07 expression was constitutive at a high level throughout growth, although the level of transcript was reduced at stationary phase when the cells were grown in defined medium. In the wild-type strain, IN07 expression was limited to a peak in the exponential phase of growth in cells grown in the absence of inositol. Interestingly, the pattern of OW7 expression in the wild- type strain resembled that of its putative target, IN07. lntracellular inositol contents of the opi7 strain were higher than those of the wild-type strain. with peak levels occurring in the stationary phase. Membrane phosphatidylinositol content paralleled intracellular inositol content, with opil strains having a higher phosphatidylinositol content in stationary phase. The proportion of the predominant phospholipid, phosphatidylcholine, exhibited a profile that was the inverse of the phosphatidylinositol content: phosphatidylcholine content was lowest in Opi7 cells in stationary phase. The Opil mutation was also found to have effects beyond phospholipid biosynthesis. opi7 cells were smaller, and Opi7 cultures achieved a cell density twice as high as comparable wild-type cultures. Opil cells were also more salt tolerant than wild-type cells: they were partly resistant to shrinking, more rapidly resumed growth, and attained a higher culture density after upshift to medium supplemented with 8% NaCl.
-
-
-
-
Roles of calcium gradients in hyphal tip growth: a mathematical model
More LessSUMMARY: A tip-high Ca2+ gradient is observed in growing fungal hyphae, but so far its role remains unknown. A mathematical model is presented, which provides evidence for the functions of such a Ca2+ gradient, in terms of its non-linear effect on the visco-elastic properties of the hyphal cytoskeleton. The model explains how the Ca2+ status at the tip may be responsible for the apical accumulation of vesicles and for an increase in the cytogel osmotic pressure, accompanied by the contraction of the cytoskeleton. The experimentally observed retraction of the spitzenkarper preceding the initiation of a branch is also reproduced, by simulating a subapical transient release of Cat+ from internal stores.
-
- Plant-Microbe Interactions
-
-
-
A functional myo-inositol catabolism pathway is essential for rhizopine utilization by Sinorhizobium meliloti
SUMMARY: Rhizopine (~-3-O-methyl-scy//o-inosamine) is a symbiosis-specif ic compound found in alfalfa nodules induced by specific Sinorhilobium meliloti strains. It has been postulated that rhizobial strains able to synthesize and catabolize rhizopine gain a competitive advantage in the rhizosphere. The pathway of rhizopine degradation is analysed here. Since rhizopine is an inositol derivative, it was tested whether inositol catabolism is involved in rhizopine utilization. A genetic locus required for the catabolism of inositol as sole carbon source was cloned from S. meliloti. This locus was delimited by transposon Tn5 mutagenesis and its DNA sequence was determined. Based on DNA similarity studies and enzyme assays, this genetic region was shown to encode an S, meliloti myo-inositol dehydrogenase. Strains that harboured a mutation in the myo-inositol dehydrogenase gene (idhA) did not display myo-inositol dehydrogenase activity, were unable to utilize myo-inositol as sole carbodenergy source, and were unable to catabolize rhizopine. Thus, myo-inositol dehydrogenase activity is essential for rhizopine utilization in s. meliloti.
-
-
- Systematics And Evolution
-
-
-
A PCR technique based on the Hipl interspersed repetitive sequence distinguishes cyanobacterial species and strains
More LessSUMMARY: The use of primers based on the Hipl sequence as a typing technique for cyanobacteria has been investigated. The discovery of short repetitive sequence structures in bacterial DNA during the last decade has led t o the development of PCR-based methods for typing, i.e. distinguishing and identifying, bacterial species and strains. An octameric palindromic sequence known as Hipl has been shown t o be present in the chromosomal DNA of many species of cyanobacteria as a highly repetitious interspersed sequence. PCR primers were constructed that extended the Hipl sequence at the 3` end by two bases. Five of the 16 possible extended primers were tested. Each of the five primers produced a different set of products when used t o prime PCR from cyanobacterial genomic DNA. Each primer produced a distinct set of products for each of the 15 cyanobacterial species tested. The ability of Hipl-based PCR to resolve taxonomic differences was assessed by analysis of independent isolates of Anabaena flos-aquae and Nostoc ellipsosporum obtained from the CCAP (Culture Collection of Algae and Protozoa, IFE, Cumbria, UK). A PCR-based RFLP analysis of products amplified from the 235-165 rDNA intergenic region was used to characterize the isolates and to compare with the Hipl typing data. The RFLP and Hipl typing yielded similar results and both techniques were able to distinguish different strains. On the basis of these results it is suggested that the Hipl PCR technique may assist in distinguishing cyanobacterial species and strains.
-
-
-
-
Phylogenetic mapping of bacterial morphology
More LessSUMMARY: The availability of a meaningful molecular phylogeny for bacteria provides a context for examining the historical significance of various developments in bacterial evolution. Herein, the classical morphological descriptions of selected members of the domain Bacteria are mapped upon the genealogical ancestry deduced from comparison of small-subunit rRNA sequences. For the species examined in this study, a distinct pattern emerges which indicates that the coccus shape has arisen and accumulated independently multiple times in separate lineages and typically survived as a persistent end-state morphology. At least two other morphologies persist but have evolved only once. This study demonstrates that although bacterial morphology is not useful in defining bacterial phylogeny, it is remarkably consistent with that phylogeny once it is known. An examination of the experimental evidence available for morphogenesis as well as microbial fossil evidence corroborates these findings. It is proposed that the accumulation of persistent morphologies is a result of the biophysical properties of peptidoglycan and their genetic control, and that an evolved body-plan strategy based on peptidoglycan may have been a fate-sealing step in the evolution of Bacteria. More generally, this study illustrates that significant evolutionary insights can be obtained by examining biological and biochemical data in the context of a reliable phylogenetic structure.
-
Volumes and issues
-
Volume 170 (2024)
-
Volume 169 (2023)
-
Volume 168 (2022)
-
Volume 167 (2021)
-
Volume 166 (2020)
-
Volume 165 (2019)
-
Volume 164 (2018)
-
Volume 163 (2017)
-
Volume 162 (2016)
-
Volume 161 (2015)
-
Volume 160 (2014)
-
Volume 159 (2013)
-
Volume 158 (2012)
-
Volume 157 (2011)
-
Volume 156 (2010)
-
Volume 155 (2009)
-
Volume 154 (2008)
-
Volume 153 (2007)
-
Volume 152 (2006)
-
Volume 151 (2005)
-
Volume 150 (2004)
-
Volume 149 (2003)
-
Volume 148 (2002)
-
Volume 147 (2001)
-
Volume 146 (2000)
-
Volume 145 (1999)
-
Volume 144 (1998)
-
Volume 143 (1997)
-
Volume 142 (1996)
-
Volume 141 (1995)
-
Volume 140 (1994)
-
Volume 139 (1993)
-
Volume 138 (1992)
-
Volume 137 (1991)
-
Volume 136 (1990)
-
Volume 135 (1989)
-
Volume 134 (1988)
-
Volume 133 (1987)
-
Volume 132 (1986)
-
Volume 131 (1985)
-
Volume 130 (1984)
-
Volume 129 (1983)
-
Volume 128 (1982)
-
Volume 127 (1981)
-
Volume 126 (1981)
-
Volume 125 (1981)
-
Volume 124 (1981)
-
Volume 123 (1981)
-
Volume 122 (1981)
-
Volume 121 (1980)
-
Volume 120 (1980)
-
Volume 119 (1980)
-
Volume 118 (1980)
-
Volume 117 (1980)
-
Volume 116 (1980)
-
Volume 115 (1979)
-
Volume 114 (1979)
-
Volume 113 (1979)
-
Volume 112 (1979)
-
Volume 111 (1979)
-
Volume 110 (1979)
-
Volume 109 (1978)
-
Volume 108 (1978)
-
Volume 107 (1978)
-
Volume 106 (1978)
-
Volume 105 (1978)
-
Volume 104 (1978)
-
Volume 103 (1977)
-
Volume 102 (1977)
-
Volume 101 (1977)
-
Volume 100 (1977)
-
Volume 99 (1977)
-
Volume 98 (1977)
-
Volume 97 (1976)
-
Volume 96 (1976)
-
Volume 95 (1976)
-
Volume 94 (1976)
-
Volume 93 (1976)
-
Volume 92 (1976)
-
Volume 91 (1975)
-
Volume 90 (1975)
-
Volume 89 (1975)
-
Volume 88 (1975)
-
Volume 87 (1975)
-
Volume 86 (1975)
-
Volume 85 (1974)
-
Volume 84 (1974)
-
Volume 83 (1974)
-
Volume 82 (1974)
-
Volume 81 (1974)
-
Volume 80 (1974)
-
Volume 79 (1973)
-
Volume 78 (1973)
-
Volume 77 (1973)
-
Volume 76 (1973)
-
Volume 75 (1973)
-
Volume 74 (1973)
-
Volume 73 (1972)
-
Volume 72 (1972)
-
Volume 71 (1972)
-
Volume 70 (1972)
-
Volume 69 (1971)
-
Volume 68 (1971)
-
Volume 67 (1971)
-
Volume 66 (1971)
-
Volume 65 (1971)
-
Volume 64 (1970)
-
Volume 63 (1970)
-
Volume 62 (1970)
-
Volume 61 (1970)
-
Volume 60 (1970)
-
Volume 59 (1969)
-
Volume 58 (1969)
-
Volume 57 (1969)
-
Volume 56 (1969)
-
Volume 55 (1969)
-
Volume 54 (1968)
-
Volume 53 (1968)
-
Volume 52 (1968)
-
Volume 51 (1968)
-
Volume 50 (1968)
-
Volume 49 (1967)
-
Volume 48 (1967)
-
Volume 47 (1967)
-
Volume 46 (1967)
-
Volume 45 (1966)
-
Volume 44 (1966)
-
Volume 43 (1966)
-
Volume 42 (1966)
-
Volume 41 (1965)
-
Volume 40 (1965)
-
Volume 39 (1965)
-
Volume 38 (1965)
-
Volume 37 (1964)
-
Volume 36 (1964)
-
Volume 35 (1964)
-
Volume 34 (1964)
-
Volume 33 (1963)
-
Volume 32 (1963)
-
Volume 31 (1963)
-
Volume 30 (1963)
-
Volume 29 (1962)
-
Volume 28 (1962)
-
Volume 27 (1962)
-
Volume 26 (1961)
-
Volume 25 (1961)
-
Volume 24 (1961)
-
Volume 23 (1960)
-
Volume 22 (1960)
-
Volume 21 (1959)
-
Volume 20 (1959)
-
Volume 19 (1958)
-
Volume 18 (1958)
-
Volume 17 (1957)
-
Volume 16 (1957)
-
Volume 15 (1956)
-
Volume 14 (1956)
-
Volume 13 (1955)
-
Volume 12 (1955)
-
Volume 11 (1954)
-
Volume 10 (1954)
-
Volume 9 (1953)
-
Volume 8 (1953)
-
Volume 7 (1952)
-
Volume 6 (1952)
-
Volume 5 (1951)
-
Volume 4 (1950)
-
Volume 3 (1949)
-
Volume 2 (1948)
-
Volume 1 (1947)