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Penttinen R, Hoikkala V, Sundberg LR. Gliding Motility and Expression of Motility-Related Genes in Spreading and Non-spreading Colonies of Flavobacterium columnare. Front Microbiol 2018; 9:525. [PMID: 29632520 PMCID: PMC5879114 DOI: 10.3389/fmicb.2018.00525] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 03/08/2018] [Indexed: 11/13/2022] Open
Abstract
Gliding motility facilitates the movement of bacteria along surfaces in many Bacteroidetes species and results in spreading colonies. The adhesins required for the gliding are secreted through a gliding motility-associated protein secretion system, known as the type IX secretion system (T9SS). The fish pathogen Flavobacterium columnare produces spreading (rhizoid [Rz], soft [S]) and non-spreading (rough [R]) colony types, of which only the spreading Rz type is virulent. In this study, we explored the spreading behavior of these colony types by microscopic imaging and measured the expression of genes associated with gliding motility and T9SS (gldG, gldH, gldL, sprA, sprB, sprE, sprF, sprT, and porV) under high and low resource levels by using RT-qPCR (reverse transcription quantitative PCR). The spreading colony types responded to the low resource level with increased colony size. The non-spreading colony type, as well as the cells growing under high nutrient level expressed only moderate cell movements. Yet, a low nutrient level provoked more active gliding motility in individual cells and increased spreading by cooperative gliding. The gene expression survey demonstrated an increased expression level of sprA (a core component of T9SS) and sprF (needed for adhesin secretion) under low nutrient conditions. Surprisingly, the expression of gliding motility genes was not consistently associated with more active spreading behavior. Furthermore, no genetic differences were found between spreading and non-spreading colony types in the studied genes associated with gliding motility. Our study demonstrates that environmental nutrient level is an important regulator of both gliding motility and the expression of some of the associated genes. These results may help to understand the connections between nutrient concentration, gliding motility, and virulence of F. columnare.
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Affiliation(s)
- Reetta Penttinen
- Centre of Excellence in Biological Interactions, Department of Biological and Environmental Science and Nanoscience Center, University of Jyväskylä, Jyväskylä, Finland
| | - Ville Hoikkala
- Centre of Excellence in Biological Interactions, Department of Biological and Environmental Science and Nanoscience Center, University of Jyväskylä, Jyväskylä, Finland
| | - Lotta-Riina Sundberg
- Centre of Excellence in Biological Interactions, Department of Biological and Environmental Science and Nanoscience Center, University of Jyväskylä, Jyväskylä, Finland
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Zhang Y, Zhao L, Chen W, Huang Y, Yang L, Sarathbabu V, Wu Z, Li J, Nie P, Lin L. Complete genome sequence analysis of the fish pathogen Flavobacterium columnare provides insights into antibiotic resistance and pathogenicity related genes. Microb Pathog 2017; 111:203-211. [DOI: 10.1016/j.micpath.2017.08.035] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2017] [Revised: 08/29/2017] [Accepted: 08/30/2017] [Indexed: 02/07/2023]
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Moore EK, Hopmans EC, Rijpstra WIC, Sánchez-Andrea I, Villanueva L, Wienk H, Schoutsen F, Stams AJM, Sinninghe Damsté JS. Lysine and novel hydroxylysine lipids in soil bacteria: amino acid membrane lipid response to temperature and pH in Pseudopedobacter saltans. Front Microbiol 2015; 6:637. [PMID: 26175720 PMCID: PMC4484230 DOI: 10.3389/fmicb.2015.00637] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 06/12/2015] [Indexed: 01/08/2023] Open
Abstract
Microbial decomposition of organic matter is an essential process in the global carbon cycle. The soil bacteria Pseudopedobacter saltans and Flavobacterium johnsoniae are both able to degrade complex organic molecules, but it is not fully known how their membrane structures are adapted to their environmental niche. The membrane lipids of these species were extracted and analyzed using high performance liquid chromatography-electrospray ionization/ion trap/mass spectrometry (HPLC-ESI/IT/MS) and high resolution accurate mass/mass spectrometry (HRAM/MS). Abundant unknown intact polar lipids (IPLs) from P. saltans were isolated and further characterized using amino acid analysis and two dimensional nuclear magnetic resonance (NMR) spectroscopy. Ornithine IPLs (OLs) with variable (hydroxy) fatty acid composition were observed in both bacterial species. Lysine-containing IPLs (LLs) were also detected in both species and were characterized here for the first time using HPLC-MS. Novel LLs containing hydroxy fatty acids and novel hydroxylysine lipids with variable (hydroxy) fatty acid composition were identified in P. saltans. The confirmation of OL and LL formation in F. johnsoniae and P. saltans and the presence of OlsF putative homologs in P. saltans suggest the OlsF gene coding protein is possibly involved in OL and LL biosynthesis in both species, however, potential pathways of OL and LL hydroxylation in P. saltans are still undetermined. Triplicate cultures of P. saltans were grown at three temperature/pH combinations: 30°C/pH 7, 15°C/pH 7, and 15°C/pH 9. The fractional abundance of total amino acid containing IPLs containing hydroxylated fatty acids was significantly higher at higher temperature, and the fractional abundance of lysine-containing IPLs was significantly higher at lower temperature and higher pH. These results suggest that these amino acid-containing IPLs, including the novel hydroxylysine lipids, could be involved in temperature and pH stress response of soil bacteria.
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Affiliation(s)
- Eli K. Moore
- Department of Marine Organic Biogeochemistry, Royal Netherlands Institute for Sea ResearchTexel, Netherlands
| | - Ellen C. Hopmans
- Department of Marine Organic Biogeochemistry, Royal Netherlands Institute for Sea ResearchTexel, Netherlands
| | - W. Irene C. Rijpstra
- Department of Marine Organic Biogeochemistry, Royal Netherlands Institute for Sea ResearchTexel, Netherlands
| | | | - Laura Villanueva
- Department of Marine Organic Biogeochemistry, Royal Netherlands Institute for Sea ResearchTexel, Netherlands
| | - Hans Wienk
- NMR Spectroscopy Research Group, Bijvoet Center for Biomolecular Research, Utrecht UniversityUtrecht, Netherlands
| | | | - Alfons J. M. Stams
- Laboratory of Microbiology, Wageningen UniversityWageningen, Netherlands
| | - Jaap S. Sinninghe Damsté
- Department of Marine Organic Biogeochemistry, Royal Netherlands Institute for Sea ResearchTexel, Netherlands
- Faculty of Geosciences, Utrecht UniversityUtrecht, Netherlands
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Vörös A, Simm R, Slamti L, McKay MJ, Hegna IK, Nielsen-LeRoux C, Hassan KA, Paulsen IT, Lereclus D, Økstad OA, Molloy MP, Kolstø AB. SecDF as part of the Sec-translocase facilitates efficient secretion of Bacillus cereus toxins and cell wall-associated proteins. PLoS One 2014; 9:e103326. [PMID: 25083861 PMCID: PMC4118872 DOI: 10.1371/journal.pone.0103326] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2014] [Accepted: 06/26/2014] [Indexed: 12/25/2022] Open
Abstract
The aim of this study was to explore the role of SecDF in protein secretion in Bacillus cereus ATCC 14579 by in-depth characterization of a markerless secDF knock out mutant. Deletion of secDF resulted in pleiotropic effects characterized by a moderately slower growth rate, aberrant cell morphology, enhanced susceptibility to xenobiotics, reduced virulence and motility. Most toxins, including food poisoning-associated enterotoxins Nhe, Hbl, and cytotoxin K, as well as phospholipase C were less abundant in the secretome of the ΔsecDF mutant as determined by label-free mass spectrometry. Global transcriptome studies revealed profound transcriptional changes upon deletion of secDF indicating cell envelope stress. Interestingly, the addition of glucose enhanced the described phenotypes. This study shows that SecDF is an important part of the Sec-translocase mediating efficient secretion of virulence factors in the Gram-positive opportunistic pathogen B. cereus, and further supports the notion that B. cereus enterotoxins are secreted by the Sec-system.
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Affiliation(s)
- Aniko Vörös
- Laboratory for Microbial Dynamics (LaMDa), Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, Oslo, Norway
| | - Roger Simm
- Laboratory for Microbial Dynamics (LaMDa), Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, Oslo, Norway
| | - Leyla Slamti
- INRA, UMR1319 Micalis, Domaine de La Minière, Guyancourt, France
| | - Matthew J. McKay
- Australian Proteome Analysis Facility (APAF), Macquarie University, Sydney, Australia
| | - Ida K. Hegna
- Laboratory for Microbial Dynamics (LaMDa), Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, Oslo, Norway
| | | | - Karl A. Hassan
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, Australia
| | - Ian T. Paulsen
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, Australia
| | - Didier Lereclus
- INRA, UMR1319 Micalis, Domaine de La Minière, Guyancourt, France
- AgroParistech, UMR Micalis, Jouy-en-Josas, France
| | - Ole Andreas Økstad
- Laboratory for Microbial Dynamics (LaMDa), Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, Oslo, Norway
| | - Mark P. Molloy
- Australian Proteome Analysis Facility (APAF), Macquarie University, Sydney, Australia
| | - Anne-Brit Kolstø
- Laboratory for Microbial Dynamics (LaMDa), Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, Oslo, Norway
- * E-mail:
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Kharade SS, McBride MJ. Flavobacterium johnsoniae chitinase ChiA is required for chitin utilization and is secreted by the type IX secretion system. J Bacteriol 2014; 196:961-70. [PMID: 24363341 PMCID: PMC3957688 DOI: 10.1128/jb.01170-13] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 12/14/2013] [Indexed: 12/15/2022] Open
Abstract
Flavobacterium johnsoniae, a member of phylum Bacteriodetes, is a gliding bacterium that digests insoluble chitin and many other polysaccharides. A novel protein secretion system, the type IX secretion system (T9SS), is required for gliding motility and for chitin utilization. Five potential chitinases were identified by genome analysis. Fjoh_4555 (ChiA), a 168.9-kDa protein with two glycoside hydrolase family 18 (GH18) domains, was targeted for analysis. Disruption of chiA by insertional mutagenesis resulted in cells that failed to digest chitin, and complementation with wild-type chiA on a plasmid restored chitin utilization. Antiserum raised against recombinant ChiA was used to detect the protein and to characterize its secretion by F. johnsoniae. ChiA was secreted in soluble form by wild-type cells but remained cell associated in strains carrying mutations in any of the T9SS genes, gldK, gldL, gldM, gldNO, sprA, sprE, and sprT. Western blot and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses suggested that ChiA was proteolytically processed into two GH18 domain-containing proteins. Proteins secreted by T9SSs typically have conserved carboxy-terminal domains (CTDs) belonging to the TIGRFAM families TIGR04131 and TIGR04183. ChiA does not exhibit strong similarity to these sequences and instead has a novel CTD. Deletion of this CTD resulted in accumulation of ChiA inside cells. Fusion of the ChiA CTD to recombinant mCherry resulted in secretion of mCherry into the medium. The results indicate that ChiA is a soluble extracellular chitinase required for chitin utilization and that it relies on a novel CTD for secretion by the F. johnsoniae T9SS.
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Affiliation(s)
- Sampada S Kharade
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, USA
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Mutations in Flavobacterium johnsoniae sprE result in defects in gliding motility and protein secretion. J Bacteriol 2011; 193:5322-7. [PMID: 21784937 DOI: 10.1128/jb.05480-11] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Cells of the gliding bacterium Flavobacterium johnsoniae move rapidly over surfaces. Transposon mutagenesis was used to identify sprE, which is involved in gliding. Mutations in sprE resulted in the formation of nonspreading colonies on agar. sprE mutant cells in wet mounts were almost completely deficient in attachment to and movement on glass, but a small percentage of cells exhibited slight movements, indicating that the motility machinery was not completely disrupted. SprE is a predicted lipoprotein with a tetratricopeptide repeat domain. SprE is similar in sequence to Porphyromonas gingivalis PorW, which is required for secretion of gingipain protease virulence factors. Disruption of F. johnsoniae sprE resulted in decreased extracellular chitinase activity and decreased secretion of the cell surface motility protein SprB. Reduced secretion of cell surface components of the gliding machinery, such as SprB, may account for the defects in gliding. Orthologs of sprE are found in many gliding and nongliding members of the phylum Bacteroidetes, suggesting that similar protein secretion systems are common among members of this large and diverse group of bacteria.
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Flavobacterium johnsoniae sprB is part of an operon spanning the additional gliding motility genes sprC, sprD, and sprF. J Bacteriol 2010; 193:599-610. [PMID: 21131497 DOI: 10.1128/jb.01203-10] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cells of Flavobacterium johnsoniae move rapidly over surfaces by a process known as gliding motility. Gld proteins are thought to comprise the gliding motor that propels cell surface adhesins, such as the 669-kDa SprB. A novel protein secretion apparatus called the Por secretion system (PorSS) is required for assembly of SprB on the cell surface. Genetic and molecular analyses revealed that sprB is part of a seven-gene operon spanning 29.3 kbp of DNA. In addition to sprB, three other genes of this operon (sprC, sprD, and sprF) are involved in gliding. Mutations in sprB, sprC, sprD, and sprF resulted in cells that failed to form spreading colonies on agar but that exhibited some motility on glass in wet mounts. SprF exhibits some similarity to Porphyromonas gingivalis PorP, which is required for secretion of gingipain protease virulence factors via the P. gingivalis PorSS. F. johnsoniae sprF mutants produced SprB protein but were defective in localization of SprB to the cell surface, suggesting a role for SprF in secretion of SprB. The F. johnsoniae PorSS is involved in secretion of extracellular chitinase in addition to its role in secretion of SprB. SprF was not needed for chitinase secretion and may be specifically required for SprB secretion by the PorSS. Cells with nonpolar mutations in sprC or sprD produced and secreted SprB and propelled it rapidly along the cell surface. Multiple paralogs of sprB, sprC, sprD, and sprF are present in the genome, which may explain why mutations in sprB, sprC, sprD, and sprF do not result in complete loss of motility and suggests the possibility that semiredundant SprB-like adhesins may allow movement of cells over different surfaces.
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Development of an efficient expression system for Flavobacterium strains. Gene 2010; 458:1-10. [PMID: 20206244 DOI: 10.1016/j.gene.2010.02.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Revised: 02/10/2010] [Accepted: 02/14/2010] [Indexed: 11/20/2022]
Abstract
Strong promoters were isolated from Flavobacterium johnsoniae in a promoter-trap vector incorporating a gfp reporter system, and were used to express fluorescent protein markers (including GFP, YFP, mOrange and mStrawberry) and insecticidal protein genes in Flavobacterium strains. Sequence analysis of trapped DNA fragments showed conserved Bacteroidetes promoter motifs (TTG-N(19)-TAnnTTTG) located upstream of putative open reading frames. Plasmids harboring these genomic DNA fragments from F. johnsoniae promoted strong production of fluorescent proteins in Flavobacterium hibernum but not in Escherichiacoli. The most potent promoter (PompA) identified in this work was cloned upstream of genes encoding fluorescent proteins, and these were co-expressed in Flavobacterium strains. The p42 and p51 genes (binary toxins from Bacillus sphaericus) when translationally fused to the 3'-end of gfp showed strong expression. Flavobacteria expressing these genes exhibited toxicity against larvae of the mosquitoes Culex quinquefasciatus, Anopheles gambiae, and Ochlerotatus triseriatus. However, transformants with the transcriptional fusion construct between cry11A with p20 from Bacillus thuringiensis did not express Cry11A protein indicating that constitutive expression of cry11A may be problematic in Flavobacterium.
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SprB is a cell surface component of the Flavobacterium johnsoniae gliding motility machinery. J Bacteriol 2008; 190:2851-7. [PMID: 18281397 DOI: 10.1128/jb.01904-07] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cells of the gliding bacterium Flavobacterium johnsoniae move rapidly over surfaces by an unknown mechanism. Transposon insertions in sprB resulted in cells that were defective in gliding. SprB is a highly repetitive 669-kDa cell surface protein, and antibodies against SprB inhibited the motility of wild-type cells. Polystyrene microspheres coated with antibodies against SprB attached to and were rapidly propelled along the cell surface, suggesting that SprB is one of the outermost components of the motility machinery. The movement of SprB along the cell surface supports a model of gliding motility in which motors anchored to the cell wall rapidly propel cell surface adhesins.
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Nelson SS, Glocka PP, Agarwal S, Grimm DP, McBride MJ. Flavobacterium johnsoniae SprA is a cell surface protein involved in gliding motility. J Bacteriol 2007; 189:7145-50. [PMID: 17644580 PMCID: PMC2045224 DOI: 10.1128/jb.00892-07] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Flavobacterium johnsoniae cells glide rapidly over surfaces by an unknown mechanism. Transposon-induced sprA mutants formed nonspreading colonies on agar, and the cells examined in wet mounts were deficient in attachment to surfaces and were almost completely nonmotile. Exposure of intact cells to proteinase K cleaved the 270-kDa SprA into several large peptides, suggesting that it is partially exposed on the cell surface.
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Affiliation(s)
- Shawn S Nelson
- Department of Biological Sciences, University of Wisconsin-Milwaukee, 3209 N. Maryland Ave., Milwaukee, WI 53211, USA
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Duchaud E, Boussaha M, Loux V, Bernardet JF, Michel C, Kerouault B, Mondot S, Nicolas P, Bossy R, Caron C, Bessières P, Gibrat JF, Claverol S, Dumetz F, Le Hénaff M, Benmansour A. Complete genome sequence of the fish pathogen Flavobacterium psychrophilum. Nat Biotechnol 2007; 25:763-9. [PMID: 17592475 DOI: 10.1038/nbt1313] [Citation(s) in RCA: 163] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2006] [Accepted: 05/29/2007] [Indexed: 11/09/2022]
Abstract
We report here the complete genome sequence of the virulent strain JIP02/86 (ATCC 49511) of Flavobacterium psychrophilum, a widely distributed pathogen of wild and cultured salmonid fish. The genome consists of a 2,861,988-base pair (bp) circular chromosome with 2,432 predicted protein-coding genes. Among these predicted proteins, stress response mediators, gliding motility proteins, adhesins and many putative secreted proteases are probably involved in colonization, invasion and destruction of the host tissues. The genome sequence provides the basis for explaining the relationships of the pathogen to the host and opens new perspectives for the development of more efficient disease control strategies. It also allows for a better understanding of the physiology and evolution of a significant representative of the family Flavobacteriaceae, whose members are associated with an interesting diversity of lifestyles and habitats.
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Affiliation(s)
- Eric Duchaud
- INRA, Unité Virologie et Immunologie Moléculaires UR892, F-78350 Jouy-en-Josas, France.
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Chen S, Bagdasarian M, Kaufman MG, Bates AK, Walker ED. Mutational analysis of the ompA promoter from Flavobacterium johnsoniae. J Bacteriol 2007; 189:5108-18. [PMID: 17483221 PMCID: PMC1951883 DOI: 10.1128/jb.00401-07] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sequences that mediate the initiation of transcription in Flavobacterium species are not well known. The majority of identified Flavobacterium promoter elements show homology to those of other members of the phylum Bacteroidetes, but not of proteobacteria, and they function poorly in Escherichia coli. In order to analyze the Flavobacterium promoter structure systematically, we investigated the -33 consensus element, -7 consensus element, and spacer length of the Flavobacterium ompA promoter by measuring the effects of site-directed mutations on promoter activity. The nonconserved sequences in the spacer region and in regions close to the consensus motifs were randomized in order to determine their importance for promoter activity. Most of the base substitutions in these regions caused large decreases in promoter activity. The optimal -33/-7 motifs (TTTG/TANNTTTG) were identical to Bacteroides fragilis sigma(ABfr) consensus -33/-7 promoter elements but lacked similarity to the E. coli sigma(70) promoter elements. The length of the spacer separating the -33 and -7 motifs of the ompA promoter also had a pronounced effect on promoter activity, with 19 bp being optimal. In addition to the consensus promoter elements and spacer length, the GC content of the core promoter sequences had a pronounced effect on Flavobacterium promoter activity. This information was used to conduct a scan of the Flavobacterium johnsoniae and B. fragilis genomes for putative promoters, resulting in 188 hits in B. fragilis and 109 hits in F. johnsoniae.
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Affiliation(s)
- Shicheng Chen
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA.
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Chen S, Bagdasarian M, Kaufman MG, Walker ED. Characterization of strong promoters from an environmental Flavobacterium hibernum strain by using a green fluorescent protein-based reporter system. Appl Environ Microbiol 2006; 73:1089-100. [PMID: 17189449 PMCID: PMC1828668 DOI: 10.1128/aem.01577-06] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We developed techniques for the genetic manipulation of Flavobacterium species and used it to characterize several promoters found in these bacteria. Our studies utilized Flavobacterium hibernum strain W22, an environmental strain we isolated from tree hole habitats of mosquito larvae. Plasmids from F. hibernum strain W22 were more efficiently (approximately 1,250-fold) transferred by electroporation into F. hibernum strain W22 than those isolated from Escherichia coli, thus indicating that an efficient restriction barrier exists between these species. The strong promoter, tac, functional in proteobacteria, did not function in Flavobacterium strains. Therefore, a promoter-trap plasmid, pSCH03, containing a promoterless gfpmut3 gene was constructed. A library of 9,000 clones containing chromosomal fragments of F. hibernum strain W22 in pSCH03 was screened for their ability to drive expression of the promoterless gfpmut3 gene. Twenty strong promoters were used for further study. The transcription start points were determined from seven promoter clones by the 5' rapid amplification of cDNA ends technique. Promoter consensus sequences from Flavobacterium were identified as TAnnTTTG and TTG, where n is any nucleotide, centered approximately 7 and 33 bp upstream of the transcription start site, respectively. A putative novel ribosome binding site consensus sequence is proposed as TAAAA by aligning the 20-bp regions upstream of the translational start site in 25 genes. Our primary results demonstrate that at least some promoter and ribosome binding site motifs of Flavobacterium strains are unusual within the bacterial domain and suggest an early evolutionary divergence of this bacterial group. The techniques presented here allow for more detailed genetics-based studies and analyses of Flavobacterium species in the environment.
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Affiliation(s)
- S Chen
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA.
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