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W F Doolittle

Publications and source records attributed to W F Doolittle.

At least 145 records · Page 8Linked to original sources
PubMed1980

Cyanobacterial plasmids: their widespread occurrence, and the existence of regions of homology between plasmids in the same and different species.

The results of screening of 29 diverse cyanobacterial (blue-green algal) strains for plasmid (CCC DNA) content are reported. Approximately one-half of the strains were shown to contain one or more CCC DNAs. CCC DNAs from four unicellular marine cyanobacteria were characterized in more detail. These strains contained multiple plasmids. Two kinds of Southern hybridization experiments allowed us to show that different plasmids within the same strain, and different plasmids within different strains, can ( but do not always) contain restricted regions of sequence homology. We suggest that these regions of homology may be analogous to the transposable genetic elements of bacterial plasmids. This, together with indirect but compelling evidence for interspecific (or intergeneric) plasmid transfer, indicates that CCC DNAs (although as yet genetically cryptic) may play a role in the ecology and evolution of obligately autotrophic prokaryotes, as they do in the ecology and evolution of the better-known heterotrophic bacteria.

Base Sequence↗
PubMed1980

Nucleotide sequences of wheat-embryo cytosol 5-S and 5.8-S ribosomal ribonucleic acids.

The nucleotide sequences of wheat embryo 5.8-S and 5-S rRNAs have been determined with the use of several techniques, including classic analysis of oligonucleotides generated by ribonuclease T1 and resolution on gels of terminally labelled RNA partially degraded with ribonucleases or with chemical reagents. The sequence of wheat embryo 5.8-S rRNA was found to be (formula: see text). This sequence is compared to 5-S rRNA sequences previously published for wheat and several other angiosperms.

Base Sequence↗
PubMed1979

The number, physical organization and transcription of ribosomal RNA cistrons in an archaebacterium: Halobacterium halobium.

Because it is now clear that archaebacteria may be as distinct from eubacteria as either group is from eukaryotic cells, and because a specifically archaebacterial ancestry has been proposed for the nuclear-cytoplasmic component of eukaryotic cells, we undertook to characterize, for the first time, the ribosomal RNA cistrons of an archaebacterium (Halobacterium halobium). We found these cistrons to be physically linked in the order 16S-23S-5S, and obtained evidence that they are also transcribed from a common promoter(s) in the order 5'-16S-23S-5S-3'. We showed that, although slightly larger immediate precursors of 16S and 23S are readily seen, no common precursor of both 16S and 23S can be easily detected in vivo. In all these respects the archaebacterium H. halobium is like a eubacterium and unlike the nuclear-cytoplasmic component of eukaryotic cells. We found, however, that it differs from eubacteria of comparable (large) genome size in having only one copy of the rRNA gene cluster per genome.

DNA, Bacterial↗
PubMed1979

Cyanobacterial evolution: results of 16S ribosomal ribonucleic acid sequence analyses.

We report here the sequences of oligonucleotides released by T1-ribonuclease digestion of the 16S ribosomal RNA's (rRNA's) of unicellular cyanobacteria Agmenellum quadruplicatum (strain BG-1) and Synechococcus 7502. We compare them with sequences previously obtained for the 16S RNA's of six other cyanobacteria and two chloroplasts, and conclude that: (i) Synechocystis-like unicells form a discrete cluster which also (and surprisingly) includes Agmenelium quadruplicatum, usually considered to be a Synechococcus; (ii) filamentous cyanobacteria of the genera Nostoc and Fischerella arose from within the Synechocystis group; (iii) phylogenetic diversity (and hence presumably evolutionary antiquity) within the Synechococcus group is very great; and (iv) red algal chloroplasts are of definite cyanobacterial origin, while Euglena chloroplasts are of separate and quite possibly noncyanobacterial origin. We also present the results of a computer-aided search among the 10 oligonucleotide 'catalogues' for families of related but nonidentical sequences. Examination of these families reinforces the above conclusions.

Base Sequence↗
PubMed1978

Ribosomal RNA homologies and the evolution of the filamentous blue-green bacteria.

Ribosomal RNA (rRNA) sequence homology (as determined by comparisons of T1 oligonucleotide catalogs of 32P-labeled 16S rRNAs) has been used to assess phylogenetic relationships within the filamentous and unicellular blue-green bacteria, and to identify regions of evolutionary conservatism within blue-green bacterial 16S rRNAs. Nostoc and Fishcherella, representatives of two morphologically distinct and highly differentiated orders, are shown to be as closely related (on the basis of RNA sequence homology) as typical members of the non-blue-green bacterial genus Bacillus. They are further shown to be (on the same basis) indistinguishable from typical unicellular members of a subgroup of the unicellular blue-green bacterial order Chroococcales. These results have general implications for studies of the origin of differentiated prokaryotes and of evolutionary change in prokaryotic macromolecules. In particular, they provide indirect evidence that the divergences of contemporary major prokaryotic groups are truly ancient ones.

Base Sequence↗
PubMed1977

Wheat embryo mitochondrial 18S ribosomal RNA: evidence for its prokaryotic nature.

We present a catalog of sequences of oligonucleotides produced by T1 ribonuclease digestion of 32P-labeled small-ribosomal-subunit RNA ("18S rRNA) isolated from purified wheat embryo mitochondria. This catalog is compared to catalogs published for prokaryotic and chloroplast 16S rRNAs and to preliminary results for wheat cytosol 18S rRNA. These comparisons indicate that: (1) wheat mitochondrial 18S rRNA is clearly prokaryotic in nature, showing significantly more sequence homology with 16S rRNAs than can be expected to arise by chance (p less than 0.000001); (2) shared oligonucleotide sequences include an especially high proportion of those identified as conserved in the evolution of prokaryotic rRNAs; and (3) wheat embryo mitochondrial and cytosol 18S rRNAs retain no more, and perhaps less, than the minimum sequence homology detectable by this sensitive method. These results argue in favor of an endosymbiotic origin for mitochondria.

Base Sequence↗
PubMed1977

Phycocyanin synthesis and degradation in the blue-green bacterium Anacystis nidulans.

Cellular content and rates of synthesis of the apoprotein subunits of phycocyanin in Anacystis nidulans cultures undergoing, and recovering from, nitrate starvation were measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of total and immunoprecipitable soluble proteins. Results indicated that (i) nitrate starvation provokes coordinate degradation of apoprotein subunits: (ii) de novo synthesis of these subunits is selectively depressed during starvation; (iii) nitrate restoration provokes coordinate increases in the rates of synthesis of these subunits, although maximal rates are not achieved for 6 to 10 h after readdition of nitrate; and (iv) illumination affects both relative and absolute rates of apoprotein formation.

Apoproteins↗
PubMed1975

On the prokaryotic nature of red algal chloroplasts.

The sequences of oligonucleotides released by T1 ribonuclease digestion of 32-P-labeled 16S (chloroplast) and 18S (cytoplasmic) ribosomal RNAs from a marine species of Porphyridium (Rhodophyta) have been determined. The resultant catalogs have been compared to those obtained for three prokaryotes:Escherichia coli, Bacillus subtilis, and Anacystis nidulans (a blud-green alga). There is extensive sequence homology between the Porphyridium chloroplast 16S ribosomal RNA and each of the prokaryotic 16S ribosomal RNAs, but little homology between the Porphyridium cytoplasmic 18S ribosomal RNA and any of the 16S species. These data provide a measure of the evolutionary distance separating existing chloroplasts from contemporary bacteria and blue-green algae, and are discussed in terms of the hypothesis that these organelles evolved from endosymbiotic photosynthetic prokaryotes.

Base Sequence↗
PubMed1975

Leucine biosynthesis in the blue-green bacterium Anacystis nidulans.

Leucine-requiring auxotrophs of the unicellular blue-green bacterium Anacystis nidulans have been isolated. Extracts of these mutants were deficient in alpha-isopropylmalate synthetase (EC 4.1.3.12). In wild-type cells, this enzyme was subject to feedback inhibition by leucine. However, formation of the enzymes of leucine biosynthesis was little affected by exogenous leucine in either wild-type or mutant strains. Cultures of the latter subjected to extreme leucine deprivation showed no change in specific activity of beta-isopropylmalate isomerase (EC 4.2.1.33) and at most a 50% increase in the specific activity of beta-isopropylmalate dehydrogenase (EC 1.1.1.85). These results are compared with others bearing on the evolution of the control of amino acid biosynthesis in blue-green bacteria.

2-Isopropylmalate Synthase↗
PubMed1974

Precursor of 5S ribosomal ribonucleic acid in the blue-green alga Anacystis nidulans.

The maturation of 5S ribosomal ribonucleic acid (rRNA) in the obligately photoautotrophic unicellular blue-green alga Anacystis nidulans has been studied by using polyacrylamide gel electrophoresis and T1 ribonuclease oligonucleotide analysis. A. nidulans mature 5S rRNA (m5) is of approximately the same molecular weight as the 5S rRNA of Escherichia coli, and is derived by cleavage of a precursor (p5) containing a few (three to six) additional nucleotides. Some of these additional nucleotides occur at the 5' end of the precursor molecule; others may occur at the 3' end. Kinetic experiments indicate that precursors of mature 5S rRNA larger than p5 either do not exist or are very transient in A. nidulans. These results are discussed in relation to those obtained with other prokaryotes.

Autoradiography↗
PubMed1974

Novel ribonucleic acid species accumulated in the dark in the blue-green alga Anacystis nidulans.

In the dark, the obligately photoautotrophic blue-green alga Anacystis nidulans accumulates large relative amounts of two novel stable ribonucleic acid species (RNAs). These species are also made in illuminated cells but are unstable in them. When darkened cells are reilluminated, these RNAs are rapidly degraded; degradation is inhibited by chloramphenicol. Upon denaturation with heat or urea, one novel species (0.33 x 10(6) daltons) dissociates into two fragments that comigrate with the second novel species (0.16 x 10(6) daltons) on polyacrylamide gels. Both RNAs are associated with particles sedimenting between 30S and 50S through sucrose gradients and are removed from these particles at low magnesium concentration. The function(s) of these RNAs remains unknown.

Cell Fractionation↗
PubMed1974

Mutational analysis of dark endogenous metabolism in the blue-green bacterium Anacystis nidulans.

We describe a mutant (strain 704) of the obligate photoautotroph Anacystis nidulans which behaves like the wild type under continuous illumination but which in the dark rapidly loses viability, respires little, and incorporates label into ribonucleic acid and protein at rates considerably less than observed with the darkened wild type. Extracts of this mutant strain show no detectable 6-phosphogluconate dehydrogenase (EC 1.1.1.44) activity. Spontaneous revertants of mutant 704 were selected as survivors of prolonged incubation in darkness. Of 10 such strains examined, none had regained 6-phosphogluconate dehydrogenase activity, and all had lost detectable glucose-6-phosphate dehydrogenase (EC 1.1.1.49) activity. Although dark survival of these revertants paralleled that of the wild type, rates of dark endogenous respiration and incorporation of labeled precursors into ribonucleic acid were still very low, comparable to those observed with strain 704. These results are consistent with the following hypotheses concerning dark endogenous metabolism in unicellular blue-green bacteria. (i) Although the oxidative pentose phosphate cycle (hexose monophosphate shunt) may play a major role in endogenous metabolism in A. nidulans, as proposed by others, it is not the only pathway capable of providing energy for maintenance of viability in darkness. (ii) Much of the endogenous metabolic activity (respiration and macromolecular synthesis) observed in darkened cultures of wild-type A. nidulans is not required for survival alone, and must therefore serve other functions.

Cell Survival↗