- Email: [email protected]
Bacterial biofilms
COMMENT Horizons A bacterial syringe
T
ype III secretory systems consist of as many as 18 components, most of which have unknown functions. Kubori et al. have purified and examined by electron microscopy a needle-like membrane component of the type III secretory system of Salmonella typhimurium. These hollow needlelike structures are embedded within the cell envelope and terminate with a round base, similar to a flagellar basal body. This similarity is not surprising, as several genes in the type III secretory locus are homologous to flagellar genes. Three components of the structure were identified by SDS-PAGE analysis to be major constituents of the secretory apparatus. Amino-
Bacterial biofilms
M
any bacteria have evolved specialized mechanisms to adhere to solid surfaces by forming glycocalyx-enriched biofilms. Pseudomonas aeruginosa can form biofilms on medical indwelling devices and in the lungs of most cystic fibrosis patients. Crucial to understanding biofilm structure and maintenance is deciphering how cells communicate within this complex community. Two cell–cell signalling systems, LasR/LasI and RhlR/RhlI (VsmR/VsmI), have been identified in P. aeruginosa. Why P. aeruginosa requires two such systems and the role(s) of each of these systems have been the subject of intense research in recent years. Davies et al. now report that LasI, which directs the synthesis of a diffusible extracellular signal [N-(3-oxododecanoyl)-Lhomoserine lactone (3OC12HSL)], plays a key role in the maintenance of P. aeruginosa biofilms. A
terminal protein sequencing revealed these to be InvG, PrgH and PrgK, which are encoded by a pathogenicity island containing the type III secretory genes. Type III secretory systems are present in a variety of bacterial pathogens. Although the signaling of protein secretion via this pathway is not well understood, this advance has identified a route by which proteins may travel across two membranes and into a neighboring cell. Kubori, T. et al. (1998) Supramolecular structure of the Salmonella typhimurium type III protein secretion system, Science 280, 602–605
Meta Kuehn e-mail: [email protected]
lasI mutant formed a uniformly thin surface layer in contrast to the thick biofilms formed by an rhlI mutant and the wild-type strain. In the presence of 3OC12HSL, the lasI biofilm was restored to normal cell density and thickness. In addition, the abnormal lasI biofilm was dispersed by exposure to 0.2% SDS, whereas a similar treatment had no detectable effect on the wild-type biofilm. Bacterial biofilms of mixed and individual species present significant economic problems in industry and medicine. Strategies designed to inhibit bacterial cell–cell signalling could aid in the control and eradication of unwanted biofilms. Davies, D.C. et al. (1998) The involvement of cell-to-cell signals in the development of a bacterial biofilm, Science 280, 295–298
Brendan Wren e-mail: [email protected]
Microbial genomics Unfinished Microbial Genomes BLAST service The National Center for Biotechnology Information (NCBI) in the USA has just made available a new BLAST service (http://www.ncbi.nlm.nih.gov/ BLAST/unfinishedgenome.html), which allows you to carry out BLAST searches for a given sequence on more than one unfinished genome at a time. You can manually select the genomes you wish to search or choose to search all 14 uncompleted genomes in one go, using BLASTN, TBLASTN or even TBLASTX. Aquifex aeolicus genome Researchers at the Diversa Corporation (San Diego, CA, USA) and their collaborators have recently reported the complete 1.55-Mb genome sequence of the thermophilic chemolithoautotrophic eubacterium Aquifex aeolicus. This remarkable microorganism is able to use an inorganic carbon source for biosynthesis and an inorganic chemical energy source, yet encodes this capability within a genome that is only one-third the size of the Escherichia coli genome. And although the microorganism grows at 958C – the extreme thermal limit of the Bacteria – there are few clues from the genome sequence as to how it does so. Also puzzling are the discordant clues from the genome sequence as to the place of Aquifex in bacterial phylogeny. The genome sequence can be viewed graphically at the NCBI (http:// www.ncbi.nlm.nih.gov/cgi-bin/ Entrez/framik?gi=133&db=Genome) or retrieved in manageable pieces via http://www.ncbi.nlm.nih.gov/ htbinpost/Entrez/query?uid=133 &form=6&db=c&Dopt=n. Diversa’s Web site is on http://www.diversa.com, with the press release describing the Aquifex aeolicus genome sequence on http://www.diversa.com/facts/ press/press.98/mar2598.html. Deckert, G. et al. (1998) The complete genome of the hyperthermophilic bacterium Aquifex aeolicus, Nature 392, 353–358
If you would like to suggest papers for inclusion in Horizons,
Mark Pallen e-mail: [email protected]
please e-mail: [email protected]
Copyright © 1998 Elsevier Science Ltd. All rights reserved. 0966 842X/98/$19.00 TRENDS
IN
MICROBIOLOGY
219
VOL. 6 NO. 6 JUNE 1998
T
ype III secretory systems consist of as many as 18 components, most of which have unknown functions. Kubori et al. have purified and examined by electron microscopy a needle-like membrane component of the type III secretory system of Salmonella typhimurium. These hollow needlelike structures are embedded within the cell envelope and terminate with a round base, similar to a flagellar basal body. This similarity is not surprising, as several genes in the type III secretory locus are homologous to flagellar genes. Three components of the structure were identified by SDS-PAGE analysis to be major constituents of the secretory apparatus. Amino-
Bacterial biofilms
M
any bacteria have evolved specialized mechanisms to adhere to solid surfaces by forming glycocalyx-enriched biofilms. Pseudomonas aeruginosa can form biofilms on medical indwelling devices and in the lungs of most cystic fibrosis patients. Crucial to understanding biofilm structure and maintenance is deciphering how cells communicate within this complex community. Two cell–cell signalling systems, LasR/LasI and RhlR/RhlI (VsmR/VsmI), have been identified in P. aeruginosa. Why P. aeruginosa requires two such systems and the role(s) of each of these systems have been the subject of intense research in recent years. Davies et al. now report that LasI, which directs the synthesis of a diffusible extracellular signal [N-(3-oxododecanoyl)-Lhomoserine lactone (3OC12HSL)], plays a key role in the maintenance of P. aeruginosa biofilms. A
terminal protein sequencing revealed these to be InvG, PrgH and PrgK, which are encoded by a pathogenicity island containing the type III secretory genes. Type III secretory systems are present in a variety of bacterial pathogens. Although the signaling of protein secretion via this pathway is not well understood, this advance has identified a route by which proteins may travel across two membranes and into a neighboring cell. Kubori, T. et al. (1998) Supramolecular structure of the Salmonella typhimurium type III protein secretion system, Science 280, 602–605
Meta Kuehn e-mail: [email protected]
lasI mutant formed a uniformly thin surface layer in contrast to the thick biofilms formed by an rhlI mutant and the wild-type strain. In the presence of 3OC12HSL, the lasI biofilm was restored to normal cell density and thickness. In addition, the abnormal lasI biofilm was dispersed by exposure to 0.2% SDS, whereas a similar treatment had no detectable effect on the wild-type biofilm. Bacterial biofilms of mixed and individual species present significant economic problems in industry and medicine. Strategies designed to inhibit bacterial cell–cell signalling could aid in the control and eradication of unwanted biofilms. Davies, D.C. et al. (1998) The involvement of cell-to-cell signals in the development of a bacterial biofilm, Science 280, 295–298
Brendan Wren e-mail: [email protected]
Microbial genomics Unfinished Microbial Genomes BLAST service The National Center for Biotechnology Information (NCBI) in the USA has just made available a new BLAST service (http://www.ncbi.nlm.nih.gov/ BLAST/unfinishedgenome.html), which allows you to carry out BLAST searches for a given sequence on more than one unfinished genome at a time. You can manually select the genomes you wish to search or choose to search all 14 uncompleted genomes in one go, using BLASTN, TBLASTN or even TBLASTX. Aquifex aeolicus genome Researchers at the Diversa Corporation (San Diego, CA, USA) and their collaborators have recently reported the complete 1.55-Mb genome sequence of the thermophilic chemolithoautotrophic eubacterium Aquifex aeolicus. This remarkable microorganism is able to use an inorganic carbon source for biosynthesis and an inorganic chemical energy source, yet encodes this capability within a genome that is only one-third the size of the Escherichia coli genome. And although the microorganism grows at 958C – the extreme thermal limit of the Bacteria – there are few clues from the genome sequence as to how it does so. Also puzzling are the discordant clues from the genome sequence as to the place of Aquifex in bacterial phylogeny. The genome sequence can be viewed graphically at the NCBI (http:// www.ncbi.nlm.nih.gov/cgi-bin/ Entrez/framik?gi=133&db=Genome) or retrieved in manageable pieces via http://www.ncbi.nlm.nih.gov/ htbinpost/Entrez/query?uid=133 &form=6&db=c&Dopt=n. Diversa’s Web site is on http://www.diversa.com, with the press release describing the Aquifex aeolicus genome sequence on http://www.diversa.com/facts/ press/press.98/mar2598.html. Deckert, G. et al. (1998) The complete genome of the hyperthermophilic bacterium Aquifex aeolicus, Nature 392, 353–358
If you would like to suggest papers for inclusion in Horizons,
Mark Pallen e-mail: [email protected]
please e-mail: [email protected]
Copyright © 1998 Elsevier Science Ltd. All rights reserved. 0966 842X/98/$19.00 TRENDS
IN
MICROBIOLOGY
219
VOL. 6 NO. 6 JUNE 1998