Scheie Anne, University of Oslo, Norway

Bacterial communication and biofilms

Anne Aamdal Scheie, Nibras A. Majeed, Jessica Lönn-Stensrud, Daniele Pecharki, Fernanda C. Petersen
Department of Oral Biology, Faculty of Dentistry, University of Oslo, Norway, e-mail a.a.scheie@odont.uio.no

In contrast to previous views, it is now appreciated that microorganisms are highly interactive, and coordinate a number of activities in response to cell density (quorum sensing). Interaction between bacteria and between bacteria and their environment is mediated by various signal molecules.
The first report on coordinated microbial group behaviour was the discovery by Tomasz that Streptococcus pneumoniae produce an extracellular hormone-like molecule that induce competence for DNA release and uptake from the environment. Later, Nealson and co-workers reported that Vibrio fisheri produce luminescence only at high cell density, but bioluminescence could be induced also at low cell density if spent medium was added. At the time, these events were thought to be unique. It was later found that gene regulation induced by inter-microbial communication is more the rule than not. Signal peptides are used by several Gram-positives and signalling via various acylated homoserine lactones (AHL) is common among Gram-negatives. Peptide and AHL communication is relatively species specific. It appears, however, that many microorganisms are bi- or multi-lingual and are able to communicate also by using the interspecies signal molecule AI-2.
Biofilm formation, virulence expression, and antimicrobial sensitivity are features regulated by microbial cell-to cell communication, thus the inter-microbial communication systems may represent attractive novel targets for control of biofilm infections. This has prompted the search for agents that may interfere with signal production, transfer or recognition. Communication interference would not affect vital microbial processes, thus the microorganisms are not likely to develop resistance against such agents.