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DNA transfer in mesophilic bacteria

Microbial life has been detected in virtually every environment on earth ranging from hydrothermal vents, salt-saturated alkaline ponds, acidic hot springs, antarctic ice, dry dessert soils, the upper atmosphere, and in animal and plant hosts. To exploit such different environments, microorganisms must have evolved phenotypic traits allowing survival under very different environmental conditions. Data obtained in studies of molecular microbial ecology and genome analyses provide growing evidence that horizontal gene transfer is a major force for bacterial adaptation to changing environments.

Despite the important impact of DNA transfer in evolution, information on the structure and function of DNA translocators is limited. To understand the mechanism of natural transformation we chose the ubiquitously distributed transformable soil bacterium Acinetobacter sp. strain BD413 and combined modern molecular, physiological, biochemical, immunological, and electron microscopical methods to analyze the structure and function of the DNA translocator. These studies led to the identification of fourteen components of the Acinetobacter transformation machinery. Interestingly several of the proteins showed significant similarities to components implicated in the biogenesis of type IV pili, dynamic structures which are essential for host cell adhesion and motility on solid surfaces of pathogenic bacteria. These similarities indicate an evolutionary relationship of transformation machineries and raised the question of an implication of the Acinetobacter pili in DNA translocation. Recently, we clearly showed that the Acinetobacter pili are not linked to DNA transport. To get insights into the function of distinct proteins of the DNA translocator we performed subcellular localization and functional interaction studies. These studies together with molecular, biochemical, and electron microscopical data led to the first model of the Acinetobacter DNA translocator (Fig. 1). Currently further studies are performed to identify novel genes of the DNA translocator in Acinetobacter and to analyze the functional interactions of the competence proteins.


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Publications 1999 - 2008

  • BUSCH, S., ROSENPLÄNTER, C. and AVERHOFF, B. 1999.
    Identification and characterization of comE and comF, two novel pilin-like competence factors involved in natural transformation of Acinetobacter sp. BD413.
    Appl. Environ. Microbiol. 65 : 4568-4574.
  • HERZBERG, C.,  FRIEDRICH, A. and AVERHOFF, B. 2000.
    comB, a novel competence gene required for natural transformation of Acinetobacter sp. BD413: identification, characterization and analysis of growth phase-dependent regulation.
    Arch. Microbiol. 173 : 220-228.
  • PORSTENDÖRFER, P., GOHL, O, MAYER, F. and AVERHOFF, B. 2000.
    ComP, a pilin-like protein essential for natural competence in Acinetobacter sp. BD413: regulation, modification by glycosylation, and cellular localization.
    J. Bacteriol. 182 : 3673-3680.
  • GOHL, O., FRIEDRICH, A. and AVERHOFF, B. 2004.
    Identification of two novel pili assembly systems in Acinetobacter sp. BD413 both unrelated to natural transformation. Appl. Environ. Microbiol. 72: 1394-1401.
  • AVERHOFF, B. 2008.
    The natural transformation system of Acinetobacter baylyi: A unique transport machinery.
    In: Acinetobacter Molecular Biology, Gerischer U (ed.) pp 119-139, Caister Academic Press, Norfolk, UK.

     

DNA transfer in extreme thermophilic bacteria

Thermophilic bacteria were found to clearly stand out in terms of interdomain DNA transfer, such as 24 and 16.2% of the genes in the hyperthermophilic bacteria Thermotoga maritima and Aquifex aeolicus, respectively, are suggested to be transferred from archaeal hyperthermophiles. Despite the massive interdomain gene transfer between hyperthermophilic archaea and bacteria until recently nothing was known with respect to the components of the transformation machineries of extremely thermophilic bacteria. To get insights into the transformation machinery of extremely thermophilic bacteria we chose the transformable strain Thermus thermophilus HB27, which was subject of whole genome sequence analysis by the Göttingen genomics laboratory. We got access to the sequence data and performed a genome based approach to search for genes involved in DNA uptake in Thermus. This approach led to the identification of the first components of the DNA transformation machinery in a thermophilic bacterium. Currently we focus on functional analyses of 16 identified proteins of the DNA translocator, and the structure, function, and regulation of the DNA translocator in Thermus. These studies shed the first light onto the structure and function of the Thermus transformation machinery and led to the first model of a DNA translocator in thermophilic bacteria (Fig. 2).


02


Further studies are underway to address the structure of the DNA translocator. Furthermore we will analyze the horizontal gene transfer between different domains, such as extremophilic archaea and bacteria, and unravel the impact of transformation systems of extremophilic bacteria in the evolution of prokaryotes.

Publications 2001 - 2006

  • FRIEDRICH, A. and AVERHOFF, B. 2001.
    Natural transformation in mesophilic and thermophilic bacteria: identification and characterization of closely related ComA-like competence factors in Acinetobacter sp. BD413 and Thermus thermophilus HB27.
    Appl. Environ. Microbiol. 67 : 3140-3148.
  • FRIEDRICH, A., PRUST, C., HARTSCH, T., HENNE, A., and AVERHOFF, B. 2002.
    Molecular analyses of the natural transformation machinery and identification of pilus structures in the extremely thermophilic bacterium Thermus thermophilus strain HB27.
    Appl. Environ. Microbiol. 68 : 745-755.
  • FRIEDRICH, A., RUMSZAUER, J., HENNE, A. and AVERHOFF, B. 2003.
    Pilin-like genes in the extremely thermophilic Thermus thermophilus HB27: Implication in competence for natural transformation and links to type IV pili biogenesis.
    Appl. Environ. Microbiol. 69 : 3695-3700.
  • FRIEDRICH, F. and AVERHOFF, B. 2003.
    Type IV pili-related natural transformation systems: DNA transport in mesophilic and thermophilic bacteria.
    Arch. Microbiol. 18 : 385-393.
  • AVERHOFF, B. 2004.
    DNA transport and natural transformation in mesophilic and thermophilic bacteria.
    J. Bioenerget. Biomembr. 36 : 25-33.
  • SCHWARZENLANDER, C., AVERHOFF, B. 2006.
    Characterization of DNA transport in the thermophilic bacterium Thermus thermophilus HB27.
    FEBS J. 273 : 4210-4218.
  • AVERHOFF, B. 2006.
    Genetic systems for Thermus.
    In Extremophiles (Methods in Microbiology), Rainey F & Oren A (eds), Vol. 35, pp 279-308, Oxford: Oxford Academic Press.
  • RUMSZAUER, J., SCHWARZENLANDER, C., AVERHOFF, B. 2006.
    Identification, subcellular localization and functional interactions of PilMNOWQ and PilA4 involved in transformation competency and pilus biogenesis in the thermophilic bacerium Thermus thermophilus HB27.
    FEBS J. 273 : 3261-3272.

     

     

Structure and function of bacterial pili

Some of the earliest events in many bacterial infections are the molecular interactions between pathogen and host cells. Many of these interactions are typically mediated by pili, which are surface appendages. Acinetobacter sp. BD413 has been shown to exhibit thin and thick pili structures. We got interested in thesepili structures since the non pathogenic soil bacterium Acinetobacter sp. BD413 is evolutionary related to Acinetobacter genomic species playing a significant role in nosocomial infections and which are of greatest importance in human medicine.

In order to analyze the Acinetobacter psp. BD413 pili structures we purified the thin and thick pili and performed genetic and molecular analyses of the pili biogenesis systems (Fig. 3).


03


Recently, we presented the first report on the pili biogenesis systems of the transformable Acinetobacter sp. BD413 and demonstrated that the thin pili are encoded by a novel chaperone-usher pili assembly system whereas a completely novel pili biogenesis cluster is required for the biogenesis of the thick pili structures. The two pili systems could play a central role in the ability of Acinetobacter sp. BD413 to attach to and form biofilms, a property that would allow them to persist in their environment. Currently we address the structure and function of these two novel Acinetobacter pili systems.

Microbial marine communities diversity (MIRACLE)

The ecosystem of the oceans is the largest in the world and their biodiversity the least well understood.  A very large part of the biosphere is located in ocean waters far from any land or interaction with terrestrial ecosystems. In the present project the problem of isolation of marine microorganisms is addressed by the use of novel methodologies, combining the fast and reliable molecular identification with strategies designed to increase the chances of retrieving novel microorganisms, whose function can be determined and also exploited for biotechnology. The potential of such hidden components of the microbial world is huge, both in terms of getting a better understanding of the ecology and physiology of microbes and to realize that potential, we must have better knowledge and understanding of microbial biodiversity and this is severely limited by the lack of cultures of the most abundant marine microbes. This project, which is supported by the European Union (MIRACLE) focuses on the sustainable development of marine resources and screening of marine microorganisms with biotechnological potential such polymer production, anti-tumor-activities, and chiral biotransformations.

 

geändert am 12. November 2010  E-Mail: Webmasterm.fauth@bio.uni-frankfurt.de

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Druckversion: 12. November 2010, 12:23
http://www.uni-frankfurt.de/fb/fb15/institute/inst-3-mol-biowiss/AK-Averhoff/research.html