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  • 1
    Electronic Resource
    Electronic Resource
    Secretion of Serratia liquefaciens phospholipase from Escherichia coli (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 8 (1993), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Serratia liquefaciens phospholipase (PhIA) is secreted to the medium from its natural host. Here we present results which indicate that, when cloned and expressed in Escherichia coli, secretion can be mediated by a putative host-encoded pathway, expression of which is controlled by FlhD (formerly FlbB), the master regulator of the flagellar/ chemotaxis regulon. In the absence of this secretion pathway, the synthesized phospholipase accumulates inside the host cell where it forms a complex with the PhlB protein. PhlB, which is encoded from the promoter distal gene of the phospholipase operon, inhibits the phospholipase activity of PhlA. Formation of this enzymatically inactive PhlA/PhlB complex is required for maintenance of cell viability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1993.tb01567.x
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  • 2
    Electronic Resource
    Electronic Resource
    Involvement of N-acyl-l-homoserine lactone autoinducers in controlling the multicellular behaviour of Serratia liquefaciens (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 20 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Several bacterial species possess the ability to differentiate into highly motile swarmer cells capable of rapid surface colonization. In Serratia liquefaciens, we demonstrate that initiation of swarmer-cell differentiation involves diffusible signal molecules that are released into the growth medium. Using high-performance liquid chromatography (HPLC), high resolution mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy, we identified N-butanoyl-l-homoserine lactone (BHL) and N-hexanoyl-l-homoserine lactone (HHL) in cell-free Serratia culture supernatants. BHL and HHL are present in a ratio of approximately 10:1 and their structures were unequivocally confirmed by chemical synthesis. The swrlswarmer initiation) gene, the predicted translation product of which exhibits substantial homology to the Luxl family of putative Nacyl homoserine lactone (AHL) synthases is responsible for directing synthesis of both BHL and HHL. In an swrl mutant, swarming motility is abolished but can be restored by the addition of an exogenous AHL. These results add swarming motility to the rapidly expanding list of phenotypes known to be controlled through quorum sensing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1996.tb02495.x
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  • 3
    Electronic Resource
    Electronic Resource
    Induction of phospholipase- and flagellar synthesis in Serratia liquefaciens is controlled by expression of the flagellar master operon flhD (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 15 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: When a liquid culture of Serratia spp. reaches the last part of the logarithmic phase of growth it induces the synthesis of several extracellular hydrolytic enzymes. In this communication we show that synthesis and secretion of the extracellular phospholipase is coupled to expression of flagella. Expression of flagella is demonstrated to follow a growth-phase-dependent pattern. Cloning, complementation studies and DNA-sequencing analysis has identified a genetic region in Serratia liquefaciens which exhibits extensive homology to the Escherichia coli flhD flagellar master operon. Interruption of the chromosomal flhD operon in S. liquefaciens results in non-flagellated and phospholipase-negative cells, but the synthesis of other exoenzymes is not affected. By placing the flhD operon under the control of a foreign inducible promoter we have shown that increased transcription through the flhD operon leads to induction of flagellar synthesis and phospholipase expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.tb02258.x
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of an Escherichia coli mutant strain resistant to the cell-killing function encoded by the gef gene family (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 6 (1992), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The chromosomal genes gef and relF from Escherichia coli and the plasmid-encoded genes hok, flmA, srnB, and pndA constitute the gef qene family, which encodes a cell-killing function. In order to investigate the mechanism of cell killing we have isolated an E. coli mutant strain that is resistant to the overexpression of the toxic proteins encoded by the gef gene family. This phenotype requires at least two mutations, one of which has been mapped to 55.2 minutes. This mutation was sequenced and shown to represent a single base substitution in an open reading frame (ORF178) encoding a putative membrane protein having a molecular mass of 20.1 kDa. ORF178 and an upstream frame, ORF190, probably constitute an operon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1992.tb01540.x
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  • 5
    Electronic Resource
    Electronic Resource
    Expression of extracellular phospholipase from Serratia liquefaciens is growth-phase-dependent, catabolite-repressed and regulated by anaerobiosis (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 6 (1992), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Many members of the genus Serratia synthesize and excrete a number of extracellular hydrolytic enzymes. One of these is the phospholipase A1 from Serratia liquefaciens, the expression of which is growth-phase-dependent. Through the use of gene fusions and primer extension analysis we show that the expression of phospholipase is subject to positive transcriptional regulation of a dual promoter system; one promoter positioned approximately 600bp upstream from the phIA gene is responsible for the induction of phospholipase expression under anaerobic conditions, and the other promoter positioned 50bp upstream from the phIA gene is subject to catabolite repression and induced during the transition from exponential to late log-phase of bacterial growth. On the basis of sequence homology and behaviour in the relevant Escherichia coli mutants, we suggest the distant promoter to be Fnr-controlled and the proximal phIA promoter to be a member of the FIbB-controlled flagellar-chemotaxis regulon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1992.tb00857.x
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  • 6
    Electronic Resource
    Electronic Resource
    Genetic analysis of functions involved in the late stages of biofilm development in Burkholderia cepacia H111 (2002)
    Oxford, UK : Blackwell Science, Ltd
    Molecular microbiology 46 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Burkholderia cepacia and Pseudomonas aeruginosa often co-exist as mixed biofilms in the lungs of patients suffering from cystic fibrosis (CF). Here, we report the isolation of 13 random mini-Tn 5 insertion mutants of B. cepacia H111 that are defective in biofilm formation on a polystyrene surface. We show that the screening procedure used in this study is biased towards mutants defective in the late stages of biofilm development. A detailed quantitative analysis of the biofilm structures formed by wild-type and mutant strains revealed that the isolated mutants are impaired in their abilities to develop a typical three-dimensional biofilm structure. Molecular investigations showed that the genes required for biofilm maturation fall into several classes: (i) genes encoding for surface proteins; (ii) genes involved in the biogenesis and maintenance of an integral outer membrane; and (iii) genes encoding regulatory factors. It is shown that three of the regulatory mutants produce greatly reduced amounts of N -octanoylhomoserine lactone (C8-HSL). This compound serves as the major signal molecule of the cep quorum-sensing system. As this density-dependent regulatory system is involved in the regulation of biofilm maturation, we investigated the interplay between the three regulatory genes and the quorum-sensing cascade. The results of these investigations show that the identified genes encode for regulatory elements that are positioned upstream of the cep system, indicating that the quorum-sensing system of B. cepacia is a major checkpoint for biofilm formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.03182.x
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  • 7
    Electronic Resource
    Electronic Resource
    Use of green fluorescent protein as a marker for ecological studies of activated sludge communities (1997)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 149 (1997), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The potential of the green fluorescent protein (GFP) as a marker gene for ecological investigations of an activated sludge community was assessed. By inserting the hybrid transposon mini-Tn5 gfp into the chromosome of Pseudomonas putida KT2442 a strongly fluorescent mutant was obtained. This strain was used for in vivo tracking of individual cells after introduction into a simple sludge microcosm. It is demonstrated that the observed reduction of introduced bacteria from sewage is mainly the result of predation by protozoa. The feasibility of combining detection of GFP fluorescence with whole cell hybridization employing fluorescently labeled, rRNA-targeted oligonucleotides in paraformaldehyde fixed samples is demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1997.tb10311.x
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  • 8
    Electronic Resource
    Electronic Resource
    Control of exoenzyme production, motility and cell differentiation in Serratia liquefaciens (1997)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 148 (1997), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Serratia liquefaciens secretes a broad spectrum of hydrolytic enzymes to the surrounding medium and possesses the ability to differentiate into specialized swarmer cells capable of rapid surface motility. Control of exoenzyme production and swarming motility is governed by similar regulatory components, including a quorum-sensing mechanism and the flagellar master operon flhDC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1997.tb10276.x
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  • 9
    Electronic Resource
    Electronic Resource
    Use of bioluminescence for monitoring the viability of individual Pseudomonas putida KT2442 cells (1997)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 149 (1997), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Exponential phase cells of Pseudomonas putida KT2442 rapidly lost viability when incubated at 0°C without entering a viable but non-culturable state. The majority of dead cells retained their cellular integrity and contained DNA. However, their cellular rRNA content was substantially reduced. By employing a luciferase-marked derivative of P. putida KT2442 in combination with a highly sensitive low-light imaging system, live and dead cells could be distinguished.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1997.tb10320.x
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  • 10
    Electronic Resource
    Electronic Resource
    Evidence of increased spread and establishment of plasmid RP4 in the intestine under sub-inhibitory tetracycline concentrations (2003)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 44 (2003), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The consequences of using anti-microbial agents in a complex ecosystem like the animal intestine can be difficult to predict. We have looked at effects of modulations in growth of competing intestinal bacteria on transfer and establishment of new genetic elements in the intestinal microflora. For this purpose, we used tetracycline, which gradually reduces the growth rate of tetracycline-sensitive bacteria, as the concentration of this drug is increased. The effect of tetracycline on transfer and establishment of the plasmid RP4, which encodes resistance to this drug, in populations of Escherichia coli BJ4 colonizing the intestine was investigated. A tetracycline-sensitive E. coli BJ4 strain was allowed to establish in the gastrointestinal tract of mice, where after an isogenic E. coli BJ4 carrying RP4 was given to the mice per os. Tetracycline in the drinking water given to the animals was kept in concentrations that allowed the sensitive recipient strain to colonize the gut. A given ‘window’ between the highest and the lowest antibiotic doses tested was shown to be optimal for the establishment of transconjugants in the intestine. These observations are important for the evaluation of the effect of a given drug on the intestinal ecosystem. A reduced potential for growth of a given bacterial species, caused by the presence of sub-inhibitory concentrations of a bacteriostatic antibiotic, will facilitate establishment of competing (i.e. closely related) organisms, which have acquired resistance genes and therefore grow well in the presence of the drug.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0168-6496(03)00016-3
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