Journal of Bacteriology
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Primer on Agar-Based Microbial Imaging Mass Spectrometry ABSTRACT
Matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) imaging mass spectrometry (IMS) applied directly to microbes on agar-based medium captures global information about microbial molecules, allowing for direct correlation of chemotypes to phenotypes. This tool was developed to investigate metabolic exchange factors of intraspecies, interspecies, and polymicrobial interactions. Based on our experience of the thousands of images we have generated in the laboratory, we present five steps of microbial IMS: culturing, matrix application, dehydration of the sample, data acquisition, and data analysis/interpretation. We also address the common challenges encountered during sample preparation, matrix selection and application, and sample adherence to the MALDI target plate. With the practical guidelines described herein, microbial IMS use can be extended to bio-based agricultural, biofuel, diagnostic, and therapeutic discovery applications.
Journal of Bacteriology - Tập 194 Số 22 - Trang 6023-6028 - 2012
Posttranscriptional control of plasmid ColIb-P9 repZ gene expression by a small RNA The replication frequency of plasmid ColIb-P9 depends on the level of repZ gene expression, which is negatively regulated by the action of the inc gene (C. Hama, T. Takizawa, H. Moriwaki, Y. Urasaki, and K. Mizobuchi, J. Bacteriol. 172:1983-1991, 1990). To further understand the mechanism of this regulation, we analyzed transcripts of the ColIb-P9 replication control region. Four RNA species, designated RNAI to RNAIV, were observed in plasmid pCH11, which contained the whole inc gene region and the 5' portion of the repZ gene. RNAII, RNAIII, and RNAIV, with sizes of approximately 200, 500, and 1,500 bases, respectively, were identified as rightward transcripts that shared common transcription initiation sites; RNAIV was determined to be equivalent to a part of repZ mRNA, which was observed in pCH10, a plasmid that contained sufficient information for replication and control of ColIb-P9. Conversely, RNAI, with a size of about 70 bases, was transcribed leftward and was identified as the product of the inc gene and hence equivalent to inc RNA detected by in vitro RNA synthesis. This small RNA was found to be complementary to a part of repZ mRNA. These results and quantitative analyses of the transcripts in Inc- mutants indicate that the inc RNA negatively regulates repZ expression mainly at the posttranscriptional level through the possible formation of an inc RNA-repZ mRNA hybrid in the host cells.
Journal of Bacteriology - Tập 172 Số 4 - Trang 1992-1997 - 1990
Organization of the replication control region of plasmid ColIb-P9 We identified a 1,845-base-pair sequence that contains essential information for the autonomous replication and regulation of the 93-kilobase-pair IncI alpha group ColIb-P9 plasmid. Biochemical and genetic analyses revealed that this sequence specifies at least two structural genes, designated repZ and inc. The repZ gene encodes a protein with a molecular weight of 39,000, which probably functions as an initiator for the ColIb-P9 replicon. The inc gene that phenotypically governs the incompatibility encodes an RNA with a size of about 70 bases. This small RNA acts in trans to repress the expression of repZ, thereby functioning to maintain a constant copy number of the ColIb-P9 replicon in host cells.
Journal of Bacteriology - Tập 172 Số 4 - Trang 1983-1991 - 1990
Nucleotide sequence and characterization of the trbABC region of the IncI1 Plasmid R64: existence of the pnd gene for plasmid maintenance within the transfer region A 6.72-kb DNA sequence between the exc gene and the oriT operon within the transfer region of IncI1 plasmid R64 was sequenced and characterized. Three novel transfer genes, trbA, trbB, and trbC, were found in this region, along with the pnd gene responsible for plasmid maintenance. The trbABC genes appear to be organized into an operon located adjacent to the oriT operon in the opposite orientation. The trbA and trbC genes were shown to be indispensable for R64 plasmid transfer, while residual transfer activity was detected in the case of R64 derivatives carrying the trbB++ deletion mutation. The T7 RNA polymerase-promoter system revealed that the trbB gene produced a 43-kDa protein and the trbC gene produced an 85-kDa protein. The nucleotide sequence of the pnd gene is nearly identical to that of plasmid R483, indicating a function in plasmid maintenance. The plasmid stability test indicated that the mini-R64 derivatives with the pnd gene are more stably maintained in Escherichia coli cells under nonselective conditions than the mini-R64 derivatives without the pnd gene. It was also shown that the R64 transfer system itself is involved in plasmid stability to a certain degree. Deletion of the pnd gene from the tra+ mini-R64 derivative did not affect transfer frequency. DNA segments between the exc and trbA genes for IncI1 plasmids R64, Colb-P9, and R144 were compared in terms of their physical and genetic organization.
Journal of Bacteriology - Tập 178 Số 6 - Trang 1491-1497 - 1996
The plasmid R64 thin pilus identified as a type IV pilus The entire nucleotide sequence of the pil region of the IncI1 plasmid R64 was determined. Analysis of the sequence indicated that 14 genes, designated pilI through pilV, are involved in the formation of the R64 thin pilus. Protein products of eight pil genes were identified by the maxicell procedure. The pilN product was shown to be a lipoprotein by an experiment using globomycin. A computer search revealed that several R64 pil genes have amino acid sequence homology with proteins involved in type IV pilus biogenesis, protein secretion, and transformation competence. The pilS and pilV products were suggested to be prepilins for the R64 thin pilus, and the pilU product appears to be a prepilin peptidase. These results suggest that the R64 thin pilus belongs to the type IV family, specifically group IVB, of pili. The requirement of the pilR and pilU genes for R64 liquid mating was demonstrated by constructing their frameshift mutations. Comparison of three type IVB pilus biogenesis systems, the pil system of R64, the toxin-coregulated pilus (tcp) system of Vibrio cholerae, and the bundle-forming pilus (bfp) system of enteropathogenic Escherichia coli, suggests that they have evolved from a common ancestral gene system.
Journal of Bacteriology - Tập 179 Số 11 - Trang 3594-3603 - 1997
NikAB- or NikB-Dependent Intracellular Recombination between Tandemly Repeated<i>oriT</i>Sequences of Plasmid R64 in Plasmid or Single-Stranded Phage Vectors ABSTRACT The origin of transfer (oriT ) of a bacterial plasmid plays a key role in both the initiation and termination of conjugative DNA transfer. We have previously shown that a conjugation-dependent recombination between the tandem R64oriT sequences cloned into pHSG398 occurred, resulting in the deletion of the intervening sequence during DNA transfer. In this study, we tandemly cloned twooriT sequences of IncI1 plasmid R64 into pUC18. Specific recombination between the twooriT sequences in pUC18 was observed withinEscherichia coli cells harboring mini-R64. This recombination was found to be independent of both therecA gene and conjugative DNA transfer. The R64 genesnikA andnikB , required for conjugal DNA processing, were essential for this recombination. Although a fully active 92-bporiT sequence was required at one site for the recombination, the 44-bporiT core sequence was sufficient at the other site. Furthermore, when twooriT sequences were tandemly cloned into the single-stranded phage vector M13 and propagated withinE. coli cells, recombination between the twooriT sequences was observed, depending on thenikB gene. These results suggest that the R64 relaxase protein NikB can execute cleavage and rejoining of single-strandedoriT DNA withinE. coli cells, whereas such a reaction in double-strandedoriT DNA requires collaboration of the two relaxosome proteins, NikA and NikB.
Journal of Bacteriology - Tập 185 Số 13 - Trang 3871-3877 - 2003
Nucleotide sequence and characterization of the traABCD region of IncI1 plasmid R64 A 3.6-kb BglII-SmaI segment of the transfer region of IncI1 plasmid R64drd-11 was sequenced and characterized. Analysis of the DNA sequence indicated the presence of four genes, traA, traB, traC, and traD, in this region. The expression of the traB, traC, and traD genes was examined by maxicell experiments and that of the traA gene was examined by constructing the traA-lacZ fusion gene. The introduction of frameshift mutations into the four genes indicated that the traB and traC genes are essential for conjugal transfer in liquid medium and on a solid surface. Both were also required for the formation of the thin pilus, which is the receptor for phages I alpha and PR64FS. Upstream of the traA gene, a promoter sequence for sigma 70 of E. coli RNA polymerase was identified by S1 nuclease mapping and primer extension experiments.
Journal of Bacteriology - Tập 175 Số 16 - Trang 5035-5042 - 1993
Characterization of a periplasmic 3':5'-cyclic nucleotide phosphodiesterase gene, cpdP, from the marine symbiotic bacterium Vibrio fischeri Vibrio fischeri, a marine bacterium that forms a bioluminescent symbiosis with certain fish and squids, exhibits the unusual attribute of growth on 3':5'-cyclic AMP (cAMP), apparently through the activity of a 3':5'-cyclic nucleotide phosphodiesterase (3':5'-CNP) with exceptionally high activity. The V. fischeri 3':5'-CNP is located in the periplasm, a novel cellular location for this enzyme in bacteria. To gain insight into the physiological function of this enzyme, we cloned the gene (designated cpdP) encoding it from V. fischeri MJ-1. This is the first bacterial 3':5'-CNP gene to be cloned. Sequencing and analysis of the 1.26-kb cpdP locus revealed a single open reading frame specifying a protein of 330 amino acid residues, including a 22-amino-acid leader peptide. The putative cpdP promoter contained a reasonable -10 promoter region (TATTAT) but contained no obvious -35 region; instead, a 12-bp inverted repeat (TTAAATATTTAA) occurred just upstream of this location. A possible rho-independent transcriptional terminator with a calculated free energy of -21.2 kcal.mol-1 (ca. -88.7 kJ.mol-1) followed the CpdP protein coding sequence. The predicted subunit molecular weight of 33,636 for the mature CpdP protein (36,087 less 2,451 for the leader peptide) was consistent with the molecular weight of 34,000 estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The deduced amino acid sequence of the CpdP protein exhibited 30.3% identity with that of the low-affinity 3':5'-CNP (PDE1) of Saccharomyces cerevisiae and 33.6% identity with that of the extracellular 3':5'-CNP of Dictyostelium discoideum. The residue identities clustered in two regions, residues 100 to 146 and 238 to 269, which contained 30 of the 33 amino acids conserved in all three proteins, 4 of which were histidines. A gene replacement mutant of V. fischeri MJ-1 containing a 0.45-kb BglII deletion within the cpdP gene lacked periplasmic 3':5'-CNP activity and did not grow on cAMP, confirming for V. fischeri the relationship among cpdP, synthesis of the periplasmic 3':5'-CNP, and growth on cAMP. The mutant exhibited no obvious sensitivity to high extracellular concentrations of cAMP (5 and 10 mM), suggesting that the enzyme does not play a role in defense against extracellular cAMP.
Journal of Bacteriology - Tập 175 Số 15 - Trang 4615-4624 - 1993
Cloning, nucleotide sequence, and expression of a gene encoding an adhesin subunit protein of Helicobacter pylori Gene hpaA, which codes for the receptor-binding subunit of the N-acetylneuraminyllactose-binding fibrillar hemagglutinin (NLBH) of Helicobacter pylori, was cloned and sequenced. The protein expressed by hpaA, designated HpaA, was identified as the adhesin subunit on the basis of its fetuin-binding activity and its reactivity with a polyclonal, monospecific rabbit serum prepared against NLBH purified from H. pylori. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis and Western blots (immunoblots) showed that the cloned adhesin has the same molecular weight (20,000) as that found on H. pylori. Also, HpaA contains a short sequence of amino acids (KRTIQK) which are all either identical or functionally similar to those which compose the sialic acid-binding motif of Escherichia coli SfaS, K99, and CFA/I. Affinity-purified antibody specific for a 12-residue synthetic peptide that included this sequence blocked the hemagglutinating activity of H. pylori and was shown by immuno-gold electron microscopy to react with almost transparent material on unstained H. pylori cells, which is consistent with previous observations concerning the location and morphology of the NLBH.
Journal of Bacteriology - Tập 175 Số 3 - Trang 674-683 - 1993
Tryptophan auxotrophs of Rhizobium japonicum Eleven tryptophan-requiring mutants of Rhizobium japonicum I-110 ARS were isolated after nitrous acid mutagenesis and fell into five groups based on characterization by supplementation with intermediates and enzyme assays.
Journal of Bacteriology - Tập 156 Số 3 - Trang 1356-1358 - 1983
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