The ultrastructure of mitotic nuclei of Blastocrithidia triatomae

The fine structure of mitotic nuclei of the flagellate Blastocrithidia triatomae has been studied by serial thin sections and three-dimensional reconstructions. The sequence of changes during the four stages of mitosis are described. A set of three dense plaques is constantly found in the equatorial stage of mitosis. The microtubular spindle is organized around these plaques. The plaques split into halves at the end of the equatorial stage, and the half-plaques migrate to the spindle ends. Elongation of the mitotic nucleus occurs after the division of the plaques. This elongation is associated with the formation of an interpolar bundle of microtubules. The equatorial spindle is formed by 26-28 microtubules and is 1.5 micrometers long. The nucleolus attaches itself to the nuclear envelope and persists up to the elongational stage; then it disintegrates and is reorganized in daughter nuclei. Mitotic events in B. triatomae are essentially similar to those in Trypanosoma cruzi epimastigotes. As in this hemoflagellate, the dense plaques behave as kinetochores. It is concluded that B. triatomae is probably a haploid organism that contains three chromosomes.

Fever: its history, cause, and function

Concepts of fever from Hippocrates to the present are briefly outlined and compared with current ideas of the pathogenesis of fever. Evidence is presented that endogenous pyrogen, the hormone that elevates body temperature, is identical with lymphocyte-activating factor, a monokine that stimulates lymphocyte proliferation and function.It now appears that inflammation and fever are closely interrelated phenomena that are modulated by a single hormone and that have been selected by evolution to protect the host against infection.

Mapping the in vivo arrangement of nucleosomes on simian virus 40 chromatin by the photoaddition of radioactive hydroxymethyltrimethylpsoralen

Intracellular simian virus 40 (SV40) chromatin was photoreacted with a 3H-labeled psoralen derivative, hydroxymethyltrimethylpsoralen (HMT), at 48 h postinfection. Psoralen compounds have been shown to readily penetrate intact cells and, in the presence of long-wavelength UV light, form covalent adducts to DNA, preferentially at regions unprotected by nucleosomes. The average distribution pattern of [3H]HMT on the SV40 genome was determined by specific activity measurements of the DNA fragments generated by HindIII plus HpaII or by AtuI restriction enzyme digestion. At levels of 1 to 10 [3H]HMT photoadducts per SV40 molecule, the radiolabel was found to be distributed nonrandomly. Comparison of the labeling pattern in vivo with that of purified SV40 DNA labeled in vitro revealed one major difference. A region of approximately 400 base pairs, located between 0.65 and 0.73 on the physical map, was preferentially labeled under in vivo conditions. This finding strongly suggests that the highly accessible region near the origin of replication, previously observed on isolated SV40 "minichromosomes," exists on SV40 chromatin in vivo during a lytic infection.

CDP-diacylglycerol synthase activity in Clostridium perfringens

CTP:phosphatidate cytidylyltransferase (CDP-diacylglycerol synthase; EC 2.7.7.41) was identified in the cell envelope fraction of the gram-positive anaerobe Clostridium perfringens. The association of this enzyme with the cell envelope fraction of cell extracts was demonstrated by glycerol density gradient centrifugation and by activity sedimenting with the 100,000 x g pellet. The enzyme exhibited a broad pH optimum between pH 6.5 and pH 7.5. Enzyme activity was dependent on magnesium (5 mM) or manganese (1 mM) ions. Activity was also dependent on the addition of the nonionic detergent Triton X-100 (5 mM). The apparent Km values for CTP and phosphatidic acid were 0.18 mM and 0.22 mM, respectively. Thioreactive agents inhibited activity, indicating that a sulfhydryl group is essential for activity. Maximal enzyme activity was observed at 50 degrees C.

DNA sequence fine-structure analysis of ilvG (IlvG+) mutations of Escherichia coli K-12

Six ilvG (IlvG+) mutations of Escherichia coli K-12 were transferred to recombinant plasmids, and the DNA sequence of each mutation was determined. This analysis confirmed that expression of the ilvG gene product (acetohydroxy acid synthase II) requires the deletion of a single base pair or the addition of two base pairs within ilvG to displace a frameshift site present in wild-type E. coli K-12. This system should be useful in the analysis of potential frameshift mutagens.

NAD metabolism in Vibrio cholerae

Extracts of Vibrio cholerae were assayed for various enzymatic activities associated with pyridine nucleotide cycle metabolism. The activities measured include NAD glycohydrolase, nicotinamide deamidase, nicotinamide mononucleotide deamidase, and nicotinic acid phosphoribosyltransferase. The results obtained demonstrate the existence in V. cholerae of the five-membered pyridine nucleotide cycle and the potential for a four-membered pyridine nucleotide cycle. The data presented also suggest that most of the NAD glycohydrolase in V. cholerae extracts is not directly related to cholera toxin.

Iron transport in Mycobacterium smegmatis: Uptake of iron from ferric citrate

In mycobacterial growth medium 40 to 400 microM citrate was required to solubilize 2 microM 55Fe. This solubilized 55Fe was taken up into both iron-deficient and iron sufficient washed cell suspensions of Mycobacterium smegmatis and Mycobacterium bovis BCG. Although the 55Fe was taken up into the cell, the citrate was not. The uptake system with M. smegmatis was not inhibited by electron transport inhibitors, uncouplers of oxidative phosphorylation, or thiol reagents and was saturable with iron at approximately 35 microM. The system was independent of the iron transport systems already known to exist in M. smegmatis: i.e., the two exochelin routes of assimilation as well as the mycobactin-salicylate system. It was not induced by the presence of 400 microM citrate in the growth medium, nor did the presence of citrate in the medium affect the production of either exochelin or mycobactin.

Effects of Petroleum Hydrocarbons on Plant Litter Microbiota in an Arctic Lake

The effects of petroleum hydrocarbons on the microbial community associated with decomposing Carex leaf litter colonized in Toolik Lake, Alaska, were examined. Microbial metabolic activity, measured as the rate of acetate incorporation into lipid, did not vary significantly from controls over a 12-h period after exposure of colonized Carex litter to 3.0 ml of Prudhoe Bay crude oil, diesel fuel, or toluene per liter. ATP levels of the microbiota became elevated within 2 h after the exposure of the litter to diesel fuel or toluene, but returned to control levels within 4 to 8 h. ATP levels of samples exposed to Prudhoe Bay crude oil did not vary from control levels. Mineralization of specifically labeled 14 C-[lignin]-lignocellulose and 14 C-[cellulose]-lignocellulose by Toolik Lake sediments, after the addition of 2% (vol/vol) Prudhoe Bay crude oil, motor oil, diesel fuel, gasoline, n -hexane, or toluene, was examined after 21 days of incubation at 10°C. Diesel fuel, motor oil, gasoline, and toluene inhibited 14 C-[lignin]-lignocellulose mineralization by 58, 67, 67, and 86%, respectively. Hexane-treated samples displayed an increase in the rate of 14 C-[lignin]-lignocellulose mineralization of 33%. 14 C-[cellulose]-lignocellulose mineralization was inhibited by the addition of motor oil or toluene by 27 and 64%, respectively, whereas diesel fuel-treated samples showed a 17% increase in mineralization rate. Mineralization of the labeled lignin component of lignocellulose appeared to be more sensitive to hydrocarbon perturbations than was the labeled cellulose component.

Cloning characterization of iaaM, a virulence determinant of Pseudomonas savastanoi

Genes for indoleacetic acid production (iaaM and iaaH) are necessary for gall induction by the olive pathogen Pseudomonas savastanoi. In strain 2009 these determinants are borne on plasmid pIAA1. To map and characterize the genes, fragments of pIAA1 generated by EcoRI endonuclease treatment were cloned in Escherichia coli by using plasmid RSF1010 as vector. We isolated a recombinant plasmid encoding iaaM, the locus for tryptophan 2-monooxygenase. This plasmid, called pLUC1, was characterized by restriction endonuclease hydrolysis. It contained a 2.75-kilobase-pair segment of pIAA1. By cloning this segment in the EcoRI site of pBR328 and pBRH3B we showed that efficient expression of iaaM was dependent on the orientation with respect to the vector promoters, and thus determined the direction of transcription. To more finely map iaaM and confirm the orientation of transcription, plasmid pLUC1 was subjected to transposon Tn/mutagenesis. The promoter-distal end of iaaM was mapped between coordinates at 1.7 and 2.15 kilobase pairs of the cloned segment.

Cloning and expression of the crystal protein genes from Bacillus thuringiensis strain berliner 1715

From a clone bank of the entire genome of Bacillus thuringiensis, one clone that contains a plasmid ( pBT 15-88) harboring a sporulation gene was identified by molecular hybridization. This gene, identified as the crystal protein gene, occurs both on a large host plasmid DNA and in the chromosomal DNA in B. thuringiensis strain berliner 1715. The inserted sequence of pBT 15-88, which corresponds to the chromosomal sequence, was not expressed in Escherichia coli. In B. thuringiensis (kurstaki), the crystal gene was found only on a large host plasmid while in B. thuringiensis ( dendrolimus ), it is only on the chromosomal DNA. The plasmid crystal gene was cloned by ligation of a 14-kb BamHI fragment of a host plasmid DNA of 42 megadaltons from strain berliner 1715 into the BamHI site of the bifunctional vector pHV33 . In E. coli and in sporulating B. subtilis the plasmid pBT 42-1 coded for a polypeptide, detected by antibodies against the crystal protein, with the same electrophoretic mobility as the crystal protein of B. thuringiensis. The crystal gene was not expressed in vegetative cells of B. subtilis, suggesting that the control at the transcriptional level is the same in B. subtilis and in B. thuringiensis. Protein extracts from the clones harboring the hybrid plasmid are toxic for the larvae of Pierris brassicae and the protein antigen forms cytoplasmic inclusion bodies in E. coli and B. subtilis, which are visible under the light microscope.

Fine structure and cytochemistry of peroxisomes (microbodies) Leptomonas samueli

Leptomonas samueli possesses in its cytoplasm a membrane-bounded organelle which can reach a length of 2.8 microns and a diameter of 0.2 microns. Catalase activity, which is inhibited by 3-amino-1, 2, 4-triazole, was detected at the ultrastructural level in the matrix of the organelle by using an alkaline diaminobenzidine medium. Freeze-fracture studies showed the presence of a large number of intramembranous particles on both the P and the E faces of the membrane of the organelle. Based on these data as well as on previous observations, it is suggested that the trypanosomatids possess an organelle that can be considered to be a peroxisome.

Carbamoyl phosphate synthetase activity from the cotyledons of developing and germinating pea seeds

Carbamoyl phosphate synthetase activity was measured in partially purified extracts from cotyledons of developing and germinating seeds of Pisum sativum L. Some properties of the enzyme were established. During cotyledon development, the activity initially increased sharply but decreased during further development. The activity from germinating seeds was only one-tenth of the maximum activity at an early developmental phase. The results are discussed in relation to pea seed development and germination.

Genetic regulation of the glyoxylate shunt in Escherichia coli K-12

The expression of the glyoxylate shunt enzymes is required for growth of Escherichia coli on acetate or fatty acids as a sole carbon source. The genes for the two unique enzymes of the glyoxylate shunt, aceA and aceB, are located at 90 min on the E. coli K-12 genetic map. Polar mutations in the aceB gene eliminate aceA gene function, suggesting that these genes constitute an operon and the direction of transcription is from aceB to aceA. Mu d (Ap lac) fusions with the aceA gene have been constructed to study the regulation of the ace operon. Expression of the ace operon is under the transcriptional control of two genes: the iclR gene, which maps near the ace operon, and the fadR gene, which maps at 25 min, and is also involved in the regulation of the fatty acid degradation (fad) regulon. Merodiploid studies demonstrated that both the iclR and fadR genes regulate the glyoxylate shunt in a trans-dominant manner.

Regulation of fatty acid composition in Escherichia coli: a proposed common mechanism for changes induced by ethanol, chaotropic agents, and a reduction of growth temperature

Growth of Escherichia coli in the presence of ethanol and chaotropic salts resulted in the synthesis of lipids containing elevated levels of unsaturated fatty acids analogous to the effect of a reduction in growth temperature. Both ethanol and chaotropic agents acted at the level of fatty acid biosynthesis and altered lipid composition by decreasing the proportion of saturated acyl chains available for the synthesis of phospholipids. A reduction in temperature causes similar effects on fatty acid biosynthesis in vivo and in vitro. Ethanol, chaotropic salts, and a decrease in temperature all weaken hydrophobic interactions. Antichaotropic salts antagonized and effects of these treatments on fatty acid synthesis in vitro. These results are consistent with a common mechanism for the effects of chaotropic agents, temperature, and ethanol on fatty acid synthesis. The biosynthesis of saturated and unsaturated acyl chains may be regulated by the strength of hydrophobic interactions. Changes in the strength of hydrophobic interactions could alter enzyme structure, substrate structure, or the equilibrium between the soluble enzymes of fatty acid synthesis and their respective acyl carrier protein substrates.

Antibody analysis of relationships among methanogenic bacteria

A bank of antisera to the majority of methanogenic bacteria is now available. Three antibody probes, R, S, and T, were derived from each antiserum in the bank and used for analysis of antigenic relatedness among methanogens by immunofluorescence. The T probe reacted only with the immunizing (or homologous) strain, the S probe gave strong cross-reactions with strains of the same species, and the R probe revealed some interspecies relationships. The results were confirmed and extended by enzyme immunoassays and standard serological methods involving serial dilution analysis, cross-adsorptions, and the use of reference strains. The immunological methods and standardized antibody probes are useful for rapid identification of methanogens and measurements of antigenic relationships which aid in the classification of these bacteria.

Specific antisera and immunological procedures for characterization of methanogenic bacteria

Specific antisera were raised in rabbits to 19 methanogenic bacteria representing the species available in pure culture at the present time. The antisera were characterized, labeled, and organized in a bank to serve as a source of material for preparation of antibody probes and thus provide standardized reagents for immunological analysis of methanogens. An indirect immunofluorescence procedure was standardized for optimal staining of homologous and heterologous bacterial strains. Two immunoenzymatic assays were developed: (i) a simple slide assay, useful for rapid antibody detection in small samples, antibody titrations, and disclosure of cross-reactions among methanogens, and (ii) a quantitative method. The latter is useful for quantification of antigenic relatedness. Procedural details were developed to obtain optimal bacterial preparations for use as immunogens to raise antibodies in vivo, and as antigens for antibody assay in vitro.

Insertion of transposons through the major cotransduction gap of Escherichia coli K-12

The major cotransduction gap of the Escherichia coli chromosome extends from mini 31 to 34. We have inserted transposons through this gap which, by sequential transduction, link sbcA (min 29.8) with manA (min 35.7) and thus eliminate the gap. These results indicate that the length of DNA in the region, as measured by transduction, is not significantly different from the length obtained by conjugational time of entry. Since this segment of the E. coli chromosome has few known genes, these transposon insertions will be useful for genetic manipulations in the region of the gap. We describe the usefulness of these markers for rapidly mapping mutations which may be isolated in the region from min 27 to 37.

Beta-lactamase-specifying plasmids isolated from Neisseria gonorrhoeae have retained an intact right part of a Tn3-like transposon

In three beta-lactamase-producing strains of Neisseria gonorrhoeae, ampicillin resistance is due to the presence of a 7.4-kilobase plasmid. Heteroduplex analysis has shown that the R plasmid contains a 1.6-kilobase segment homologous to the right part (the region coding for the beta-lactamase) of the Tn3-like transposon Tn2301 the 1.6-kilobase DNA segment is not transposable, but it can give rise to a functional transposon, when linked to the left part of TN2301. This provides strong evidence that the R plasmids of N. gonorrhoeae are deletion derivatives of a plasmid that contained an entire TN3-like transposon.

The immunology of mycobacterial infections

Mycobacteria are endowed with substances that profoundly affect the immune system. Leprosy and tuberculosis exemplify broad spectra of useful and detrimental immune responses of mycobacterial infections that range from intense potentiation to severe specific adn nonspecific suppression of humoral and cellular immune elements. The cellular hypersensitivity induced by mycobacteria serves as a classical model for the analysis of specific and nonspecific immune mechanisms. Mycobacterial disease are prevalent worldwide and rank among the most important bacterial diseases. The kaleidoscope of immunologic events induced by injected mycobacteria and during infections will be reviewed from the standpoint of pathogenesis, pathology, in vitro and in vivo effects on cellular and humoral arms of the immune response, diagnosis, classification, potentiation and suppression.

Failure of bacterial lipopolysaccharide to elicit a cytostatic effect on Plasmodium vinckei petteri in C3H/HeJ mice

Malarial parasites, Plasmodium vinckei petteri, taken from lipopolysaccharide (LPS) high-responder (C3H/HeJGiFWeHi) mice which had been injected 7 to 8 h previously with either Escherichia coli LPS B or LPS W incorporated the purine nucleotide precursor hypoxanthine more slowly in an in vitro assay than parasites taken from saline-injected controls. In contrast, malarial parasites taken from LPS low-responder C3H/HeJ mice after injection of either LPS B or LPS W did not show reduced levels of hypoxanthine incorporation. These differing results with LPS high- and low-responder mouse strains demonstrated that the cytostatic effect on the parasites seen in the high-responder strain was not due to the direct action of LPS and implied that the cytostasis was mediated via host lymphoreticular cells. Furthermore, the failure of LPS B, a lipid A-associated protein-containing LPS preparation, to elicit a cytostatic effect on P. vinckei petteri in C3H/HeJ mice suggested that the LPS-induced effector mechanisms acting against malarial parasites may be similar to those reported against bacteria and tumors.

Fever and immunoregulation: hyperthermia, interleukins 1 and 2, and T-cell proliferation

The role of fever in host defense, if indeed it has one, is poorly understood. Fever in response to exogenous agents is mediated by a host macrophage product called endogenous pyrogen (EP). Recently it has been shown that EP is probably identical to interleukin 1 (IL1), an immunostimulatory macrophage product that induces T-cell proliferation. We postulated that the pyrogenic and immunostimulatory actions of this host mediator might be interrelated and tested T-cell proliferation induced by IL1 at a temperature characteristic of fever. The T-cell proliferative response to IL1 (and to the lymphokine, interleukin 2) was greatly increased at 39 degrees C compared to 37 degrees C, while B-cell mitogenesis in response to lipopolysaccharide was not. These findings suggest that, if similar events occur in vivo, fever may have important immunoregulatory significance and call into question the current indiscriminate use of antipyretic agents.

Taxonomic studies on Filobasidiella species and their anamorphs

The taxonomy of Filobasidiella neoformans Kwon-Chung and F. bacillispora Kwon-Chung and their anamorphs were reinvestigated. Although the cross between the type culture of the two species failed to produce viable basidiospores, another pair of isolates did yield viable basidiospores. The segregation of phenotypic markers among the tetrads isolated from this inter specific cross proved that meiosis had occurred. On the basis of other previously known differences and the present genetic study, the two species are now considered to be two varieties of the species, F. neoformans. The anamorph of F. neoformans var. neoformans grew well at 37 degrees C in vitro and produced fatal infection in mice while that of F. neoformans var. bacillispora grew poorly at 37 degree C and failed to produce fatal infection in mice. Cryptococcus bacillisporus Kwon-Chung et Bennett is regarded as a synonym of C. neoformans var. gattii Vanbreuseghem et Takashio.

Positive coooperativity in the binding of Streptococcus sanguis to hydroxylapatite

The adherence of Streptococcus sanguis to hydroxylapatite beads has been analyzed by binding isotherms, Langmuir isotherms, and Scatchard plots. For saliva-coated beads, the Scatchard curves contained components with both positive and negative slopes. The results are interpreted as evidence for positive cooperativity in the binding process. Although all Scatchard curves were similar in shape, distinct differences were observed between saliva samples from different individuals. Salivary agglutinins against whole S. sanguis cells did not appear to influence the shapes of the curves or the extent of adherence. In addition, different strains of S. sanguis yielded similar Scatchard plots. When the binding of S. sanguis to buffer-coated hydroxylapatite beads was analyzed by Scatchard plots or binding isotherms, curves were generated which suggested that either direct ligand-ligand or nonspecific interactions were occurring. Hill plots of the adherence data yielded curves with slopes greater than unity for saliva-coated beads, providing additional support for the view that the interactions between S. sanguis and the pellicle involve cooperative phenomena. In contrast, a Hill plot for the binding data of S. sanguis to buffer-coated hydroxylapatite beads gave a curve with a slope of 0.91 +/- 0.07, suggesting negative cooperativity or limited specificity. When adherence data were plotted by the Langmuir method, curves were obtained which could not discriminate between the binding of the bacteria to the hydroxylapatite beads coated with either saliva or buffer. It was also observed that several different proteins and whole saliva tended to inhibit adherence. Scatchard plots, however, describing the binding of S. sanguis to the proteincoated beads were unique and revealed possible specific and nonspecific interactions. Scatchard analyses of binding data may be useful in understanding the mechanism(s) of adherence of streptococci to smooth surfaces.

Permissiveness of rabbit monocytes and macrophages for herpes simplex virus type 1

The permissiveness of rabbit monocytes and macrophages for herpes simplex virus was examined. Peripheral blood monocytes, alveolar macrophages, and peritoneal exudate macrophages were studied for their ability to replicate herpes simplex virus strains RE and KOS. Results indicated different degrees of interaction with virus depending on the macrophage type. Only peritoneal exudate macrophages showed evidence of virus replication. Productive infection was limited, with only a small number of cells (0.02%) yielding infectious virus. Higher numbers of cells appeared to be abortively infected. Approximately 40% expressed antigens, whereas virtually all were killed by exposure to virus. Coreless particles were seen by electron microscopy in about one-third. Alveolar macrophages were also killed by virus and showed evidence of virus adsorption, but showed no indication of productive or abortive infection. Monocytes neither adsorbed nor replicated virus, and viability was unaffected. Results suggest that differences in degrees of cellular maturation or differentiation, or both, account for the spectrum of interactions seen between herpes simplex virus and rabbit macrophages.

Isolation of Methanobrevibacter smithii from human feces

Fecal specimens from nine adults were examined for the presence of methanogenic bacteria. Enrichment cultures of five specimens produced methane in 5 days. Of these five specimens, three were tested and produced methane during a short-term incubation. Four specimens did not produce methane in either short-term incubation or in enrichment culture. Each methanogenic culture contained methanogens similar in morphology to organisms of the genus Methanobrevibacter and showed factor-420 fluorescence by fluorescence microscopy. Pure cultures were obtained from four of the five methanogenic enrichment cultures. Each isolate grew and formed methane from either H2-CO2 or formate, but growth obtained with formate was poor. None of the isolates used acetate, methanol, or trimethylamine. All isolates grew in the presence of bile salts. In immunological studies, each isolate was closely related to the type strain of Methanobrevibacter smithii, a finding consistent with the physiological and morphological similarities between the isolates and the type strain.

Dominant mutators in Escherichia coli

In this paper we report on the isolation and genetic analysis of a series of strong mutators mapping at five minutes on the E. coli chromosome. These mutations are dominant and show no evidence of interaction in merodiploids. Cultures grown in broth medium exhibit mutant frequencies five to six orders of magnitude higher than mut+ strains. Cultures propagated in minimal salts media mutate at rates one to three orders higher than wild-type. Three-factor crosses have been used to order these mutators relative to metD, proA, and a Tn10 insertion near five minutes.

Cleavage sites within the poliovirus capsid protein precursors

Partial amino-terminal sequence analysis was performed on radiolabeled polio-virus capsid proteins VP1, VP2, and VP3. A computer-assisted comparison of the amino acid sequences obtained with that predicted by the nucleotide sequence of the poliovirus genome allows assignment of the amino terminus of each capsid protein to a unique position within the virus polyprotein. Sequence analysis of trypsin-digested VP4, which has a blocked amino terminus, demonstrates that VP4 is encoded at or very near to the amino terminus of the polyprotein. The gene order of the capsid proteins is VP4-VP2-VP3-VP1. Cleavage of VP0 to VP4 and VP2 is shown to occur between asparagine and serine, whereas the cleavages that separate VP2/VP3 and VP3/VP1 occur between glutamine and glycine residues. This finding supports the hypothesis that the cleavage of VP0, which occurs during virion morphogenesis, is distinct from the cleavages that separate functional regions of the polyprotein.

Genetic analysis of bacteriophage T4 transducing bacteriophages

Mutations in the genes for nuclear disruption (ndd), endonuclease IV (denB), and the D1 region of the T4 genome are essential for converting bacteriophage T4 into a generalized transducing phage. These mutations gave rise to a very low frequency of transduction, about 10(-8) per infected bacterium. The addition of an rII mutation raised the transduction frequency about 20-fold. An additional 100-fold increase in the transduction frequency was observed with mutations in genes 42, 56, and alc. High-frequency generalized transduction by T4 results from the cumulative effect of these mutations.

Spontaneous protoplast formation in Methanobacterium bryantii

Methanobacterium bryantii was found to undergo rapid lysis when grown in a prereduced chemically defined medium under H2-CO2 (4:1, vol/vol). The addition of 20 mM MgCl2 to the medium gave, rather than rapid lysis, a gradual formation of phase-dark spherical bodies which in thin section appeared as true protoplasts. In general, the protoplasts were stabilized by divalent but not monovalent cations and, unlike whole cells, were sensitive to lysis by Triton X-100. Electron microscopic examination revealed that protoplast formation was preceded by a general breakdown of the cell wall with an apparent squeezing out of the protoplast through the degraded wall. The growth of cells was greatly increased and not accompanied by detectable lysis in a medium modified by elevating the levels of nickel and ammonium.

Energization of the transport systems for arabinose and comparison with galactose transport in Escherichia coli

1. Strains of Escherichia coli were obtained containing either the AraE or the AraF transport system for arabinose. AraE+,AraF- strains effected energized accumulation and displayed an arabinose-evoked alkaline pH change indicative of arabinose-H+ symport. In contrast, AraE-,AraF+ strains accumulated arabinose but did not display H+ symport. 2. The ability of different sugars and their derivatives to elicit sugar-H+ symport in AraE+ strains was examined. Only L-arabinose and D-fucose were good substrates, and arabinose was the only inducer. 3. Membrane vesicles prepared from an AraE+,AraF+ strain accumulated the sugar, energized most efficiently by the respiratory substrates ascorbate + phenazine methosulphate. Addition of arabinose or fucose to an anaerobic suspension of membrane vesicles caused an alkaline pH change indicative or sugar-H+ symport on the membrane-bound transport system. 4. Kinetic studies and the effects of arsenate and uncoupling agents in intact cells and membrane vesicles gave further evidence that AraE is a low-affinity membrane-bound sugar-H+ symport system and that AraF is a binding-protein-dependent high-affinity system that does not require a transmembrane protonmotive force for energization. 5. The interpretation of these results is that arabinose transport into E. coli is energized by an electrochemical gradient of protons (AraE system) or by phosphate bond energy (AraF system). 6. In batch cultures the rates of growth and carbon cell yields on arabinose were lower in AraE-,AraF+ strains than in AraE+,AraF- or AraE+,AraF+ strains. The AraF system was more susceptible to catabolite repression than was the AraE system. 7. The properties of the two transport systems for arabinose are compared with those of the genetically and biochemically distinct transport systems for galactose, GalP and MglP. It appears that AraE is analogous to GalP, and AraF to MglP.

Iron uptake and iron limited growth of Escherichia coli K-12

Cells of Escherichia coli K-12 could grow aerobically at an iron concentration as low as 0.05 micrometer without any of the known iron ionophores present. The growth rate increased between 0.05 and 2 micrometer iron. Supplementation with the iron ligands ferrichrome and citrate resulted in optimal growth already at 0.05 micrometer iron. Under certain conditions iron uptake preceded growth of cells by more than an hour. During logarithmic growth the rate of iron uptake matched the growth rate. The radioactive tracer method revealed a cellular iron content of 4 nmol/mg dry weight. After consumption of the iron in the medium cells continued to grow with high rate for 1-2 generations. The iron uptake activity was increased during iron starvation.

Molecular cloning of the uvrD gene of Escherichia coli that controls ultraviolet sensitivity and spontaneous mutation frequency

The uvrD gene of Escherichia coli that controls UV sensitivity and spontaneous mutation frequency has been cloned with phage lambda as vector. The increased sensitivity to ultraviolet light (UV) of uvrD3, uvrE502, recL152, and pdeB41 mutants, high mutability of uvrD3 and pdeB41 mutants, and conditional lethality of strain TS41 that carried pdeB41, polA1, and supl26 mutations were all suppressed by lysogenization of the mutant cells with lambda uvrD+. These results were consistent with the idea that the uvrD, uvrE, recL, and pdeB mutations are alleles of the uvrD gene. In addition to the uvrD gene, lambda uvrD+ carried the corA gene that controls transport of Mg++, Mn++, and Co++ through the cell membrane. Hybrid plasmids carrying both uvrD and corA genes were also constructed by using pKY2289 as a cloning vehicle. Orientational isomers that carried the same 12.0 kb fragment in the opposite direction were equally efficient in complementing the UvrD- as well as CorA- defects of the transformed host cells, suggesting that the DNA insert contains all the genetic signals needed to express the two gene products. Insertion of the gamma delta sequence into recombinant plasmids was performed to generate appropriate restriction endonuclease target sites in the cloned DNA fragments.

Methane-oxidizing microorganisms

Images

Cloning and the nucleotide sequence of the genes for Escherichia coli ribosomal proteins L28 (rpmB) and L33 (rpmG)

The specialized transducing bacteriophage lambda dpyrE DNA was used as a source of DNA to clone two ribosomal protein genes rpmB (L28) and rpmG (L33) on the cloning vehicle pACYC184. Using one of these plasmids, the nucleotide sequence of these two genes and their flanking regions were determined. The amino acid sequences of both proteins deduced from the nucleotide sequences match with the amino acid sequences previously determined, with one exception. The nucleotide sequences suggest that these two ribosomal protein genes are cotranstribed. There was no expression of the second gene of the operon, rpmG, in the absence of the 5' sequences adjacent to the first gene, rpmB. Observation of the structure of mRNA also strongly supports the idea that rpmB and rpmG are in a single transcription unit whose order is: rpmBp-rpmB-rpmG-rpmGt.

Proton translocation coupled to trimethylamine N-oxide reduction in anaerobically grown Escherichia coli

Proton translocation coupled to trimethylamine N-oxide reduction was studied in Escherichia coli grown anaerobically in the presence of trimethylamine N-oxide. Rapid acidification of the medium was observed when trimethylamine N-oxide was added to anaerobic cell suspensions of E. coli K-10. Acidification was sensitive to the proton conductor 3,5-di-tert-butyl-4-hydroxybenzylidenemalononitrile (SF6847). No pH change was shown in a strain deficient in trimethylamine N-oxide reductase activity. The apparent H+/trimethylamine N-oxide ratio in cells oxidizing endogenous substrates was 3 to 4 g-ions of H+ translocated per mol of trimethylamine N-oxide added. The addition of trimethylamine N-oxide and formate to ethylenediaminetetraacetic acid-treated cell suspension caused fluorescence quenching of 3,3'-dipropylthiacarbocyanine [diS-C3-(5)], indicating the generation of membrane potential. These results indicate that the reduction of trimethylamine N-oxide in E. coli is catalyzed by an anaerobic electron transfer system, resulting in formation of a proton motive force. Trimethylamine N-oxide reductase activity and proton extrusion were also examined in chlorate-resistant mutants. Reduction of trimethylamine N-oxide occurred in chlC, chlG, and chlE mutants, whereas chlA, chlB, and chlD mutants, which are deficient in the molybdenum cofactor, could not reduce it. Protons were extruded in chlC and chlG mutants, but not in chlA, chlB, and chlD mutants. Trimethylamine N-oxide reductase activity in a chlD mutant was restored to the wild-type level by the addition of 100 microM molybdate to the growth medium, indicating that the same molybdenum cofactor as used by nitrate reductase is required for the trimethylamine N-oxide reductase system.

Bacteriophage T4 alc gene product: general inhibitor of transcription from cytosine-containing DNA

The alc gene of bacteriophage T4 was originally defined on the basis of mutations which allow late protein synthesis directed by T4 DNA containing cytosine rather than hydroxymethylcytosine. The question remained whether the normal alc gene product (gpalc) also blocks the transcription of early genes from cytosine-containing DNA. Complementation experiments were performed between hydroxymethylcytosine-containing phage which direct gpalc synthesis but carry mutations in a given gene(s) and cytosine-containing phage carrying that gene(s). The required protein would then have to be directed by the cytosine-containing DNA: it is looked for directly on polyacrylamide gels or through its physiological effects or both. For all early proteins examined in this way, no synthesis was observed when 95 to 100% of the hydroxymethylcytosine was substituted by cytosine in the infecting DNA, whereas there was significant synthesis with 75% substitution or less. The results indicate that gpalc is carried in with the infecting DNA or is made very early to block transcription of all cytosine-containing DNA.

Trichosporonoides nigrescens sp. nov., a new xerophilic yeast-like fungus

A new yeast-like fungus isolated from jam on two occasions is described as Trichosporonoides nigrescens. It is a true xerophile, able to grow at water activities at least as low as 0.75. For this reason, its carbon assimilation pattern was examined using both dilute (standard) and concentrated carbon sources: six to nine compounds not assimilated at the standard concentrations of 0.5% (0.001 to 0.1 mol/kg) were assimilated at 1.5 to 2.0 mol/kg. Cell wall and septal ultrastructure, DNA base ratios, and the nuclear cycle were examined to determine the generic and higher taxonomic affinities of this microorganism. All properties were consistent with its assignment to Trichosporonoides Haskins et Spencer. However, while ultrastructure indicated an affinity with the Basidiomycetes, the mitotic nuclear cycle and the xerophilic nature of this fungus suggested an Ascomycete affinity. The GC content (57%) is consistent with assignment to either. No teleomorphic state was found.

Valine-resistant Escherichia coli K-12 strains with mutations in the ilvB operon

Escherichia coli K-12 mutants resistant to growth inhibition by valine were isolated. These strains contained mutations in the ilvB operon effecting either the regulation of acetohydroxy acid synthase I or the sensitivity of the enzyme to end product inhibition by valine.

Analysis of age-dependent resistance to murine coronavirus JHM infection in mice

Resistance to intraperitoneal murine coronavirus JHM infection in mice develops with age. C3H mice were found to be fully susceptible up to the age of 20 days and resistant after 23 days of age. Protection of susceptible animals from death due to infection could be achieved by maternal antibodies or by transfer of spleen cells from immunized, but not from nonimmunized, donor mice. Lack of protection by transfer of unprimed adult spleen cells was not related to immunosuppression by the host. Moreover, resistance of adult mice could not be abrogated by application of lymphocytes from suckling mice, although immune suppression by other means did affect the resistance of adult animals. On the other hand, spleen cells from nonimmunized mice could be primed with inactivated JHM virus in suckling mice and protected these mice from death due to a subsequent virus infection. Thus, the outcome of infection with JHM virus in suckling and adult mice can be influenced by immunological events, but is not exclusively due to the different stages of immune competence.

Plasmid-directed synthesis of enzymes required for D-mannitol transport and utilization in Escherichia coli

A transformant Escherichia coli colony bank [Clarke, L. & Carbon, J. (1976) Cell 9, 91-99] has been screened for hybrid ColE1 plasmids carrying the genes for D-mannitol utilization. Two of the plasmids, pLC11-7 and pLC15-48, were shown to contain the mannitol operon, which includes the structural genes for the mannitol-specific enzyme II of the phosphotransferase system and mannitol-1-phosphate dehydrogenase. One E. coli strain harboring plasmid pLC15-48 overproduced mannitol-1-phosphate dehydrogenase activity 4- to 5-fold. However, there was no corresponding increase in mannitol enzyme II activity. Plasmid pLC15-48 was shown to direct the synthesis of two polypeptides in E. coli minicells in the presence of cyclic AMP and mannitol. The larger (Mr = 60,000) was membrane bound and was specifically precipitated by antibody directed against purified mannitol-specific enzyme II. The smaller (Mr = 40,000) was soluble and had an electrophoretic mobility indistinguishable from that of the major component in a partially purified mannitol-1-phosphate dehydrogenase preparation. These data are consistent with previous genetic studies of the mannitol locus and confirm an independent conclusion [Jacobson, G. R., Lee, C. A. & Saier, M. H., Jr. (1979) J. Biol. Chem. 254, 249-252] that mannitol enzyme II consists of a single type of polypeptide chain that has a Mr of 60,000. The plasmid pLC15-48 DNA was characterized by mapping of restriction endonuclease cleavage sites.

Immunodiffusion method for detection of type A Clostridium botulinum

A simple gel immunodiffusion agar procedure was developed for detecting toxigenic strains of Clostridium botulinum type A. The method consisted of overlaying colonies grown on thin-layer tryptone-peptone-glucose-yeast extract agar with gel diffusion agar containing desired levels of C. botulinum type A antitoxin. Concentric precipitin zones formed around colonies of C. botulinum type A. Strains of C. botulinum type A were detected by this procedure. However, C. botulinum type B reacted to a lesser degree with this system. No reaction was noted with types E, F, Langeland, F8G, Clostridium perfringens, or with strains of nontoxigenic Clostridium sporogenes. Thickness of the plating medium, incubation time and temperature, environmental growth conditions, and levels of both agar an antitoxin were important factors affecting the efficiency of the procedure, whereas the age of the culture (used as inoculum) was not critical. Thin agar medium (5 ml per plate [15 by 100 mm]) containing 1.5% agar gave consistent results, but more agar limited diffusion, and lower levels encouraged spreaders. The optimal concentration of antitoxin incorporated in to the gel diffusion agar overlay was 1.2 IU/ml gel diffusion agar. Rabbit type A antitoxin prepared with purer immunizing agent gave similar reactions. The addition of type A antitoxin in tryptone-peptone-glucose-yeast extract agar medium before inoculation with type A C. botulinum showed promising results.