Tag Archives: Science

Walking with bacteria

They swim, they swarm, they twitch and glide…they even ride on comet tails, and now it seems that bacteria can ‘walk’ as Maxsim Gibiansky and colleagues demonstrate in their short but sweet research published in Science.

Gibiansky et al. studied the behaviour of Pseudomonas aeruginosa, a bacteria that is ordinarily found in soil and water, but has increasingly been associated with opportunistic infections in humans (and is a particular problem in those with cystic fibrosis). A key feature of P. aeruginosa is that these bacteria form multicellular, surface-bound communities called biofilms and are able to move within these communities by twitching motility owing to their type IV pili (hair-like structures on bacteria that can extend, tether to a surface and then retract to move bacteria along). The researchers studied microscopy movies of the P. aeruginosa biofilms and used computer software to track how the bacteria transitioned from planktonic state (that is, freely suspended in liquid) to the surface-bound biofilm.

Two different surface motility mechanisms were observed just after P. aeruginosa bacteria attached to a surface, but before a microcolony of bacteria were formed. The scientists studied mutant bacteria lacking flagella (a tail-like bacterial appendage that can also enable bacteria to move) that can only move using their type IV pili. These bacteria tended to ‘crawl’ in one direction when positioned horizontal to the surface and ‘walked’ in all directions when attached vertically to the surface by one end of the bacteria. Each movement mechanism was useful for surface exploration; crawling enabled directional movement across larger areas (6 μm distance) than walking, which enabled rapid exploration in local areas (up to 2 μm distance). Furthermore, these same movements were observed in wild-type bacteria. Moreover, the orientation of bacteria influenced biofilm morphology. Surface detachment was facilitated by type IV pili by tilting bacteria from horizontal to vertical positions and after bacterial division newborn bacteria detach and then ‘walk’ away. Finally, bacteria lacking type IV pili could neither ‘crawl’ or ‘walk’.

Scientific observations like this brevia report add to the understanding of bacterial behaviour in biofilms and could eventually lead to useful, new treatments against biofilm-forming pathogens.


ResearchBlogging.orgGibiansky, M., Conrad, J., Jin, F., Gordon, V., Motto, D., Mathewson, M., Stopka, W., Zelasko, D., Shrout, J., & Wong, G. (2010). Bacteria Use Type IV Pili to Walk Upright and Detach from Surfaces Science, 330 (6001), 197-197 DOI: 10.1126/science.1194238

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Filed under Microbiology

Mapping our microbes

Researchers have successfully mapped the different microbial communities over the whole body according to research by Costello and colleagues published in Science this week.

The human body is home to trillions of bacteria, so many that in fact bacteria outnumber our own cells by 10 to 1. The human body’s microbiota (the microorganisms that live inside or on our body) is often diverse and complex. It is important to examine the different communities of bacteria that live in association with a healthy human body so that we can better understand how these microorganisms affect our health.

The researchers assessed the diversity of bacteria in different habitats on the body, in different people and whether these bacterial communities changed over time. Over the course of three months, the researchers surveyed and sequenced the different bacteria from up to 27 human body sites – including the ear canal, gut, mouth and skin – in seven to nine healthy adults. They found that bacterial communities were defined by their location on the body. Some body sites, like the back of the knee or the gut, have many different types of bacteria living there whilst places like the navel or forehead have very few types of bacteria. These bacterial communities within each habitat varied little over time in individuals. Surprisingly, some skin sites – including the forearm, palm, index finger and back of the knee – had a greater diversity of bacteria compared with the gut and the mouth (body sites known to harbour many different types of bacteria). The researchers then “transplanted” bacteria from one site on the body to another (after sterilisation) and monitored which bacteria grew to test whether some parts of the body were more hospitable to bacteria than others. For instance, tongue bacteria could grow on a person’s forearm but not on their forehead and similar results were achieved when transplanting one person’s tongue bacteria onto another person’s forearm or forehead. Finally, the researchers found that different people had very different types of bacteria living on them (we have our own personalised set of microorganisms living on us).

Further work is needed to survey the human microbiota of more people and how it changes over a longer period of time. Studies like the Human Microbiome Project will help to map the microbes of many more people and further our understanding of the microbial factors which are associated with health and disease.

Costello, E., Lauber, C., Hamady, M., Fierer, N., Gordon, J., & Knight, R. (2009). Bacterial Community Variation in Human Body Habitats Across Space and Time Science, 326 (5960), 1694-1697 DOI: 10.1126/science.1177486

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Filed under Microbiology, Science