Biofilms Beckon
Research concentration by microbiologists on the hugely successful "pure culture paradigm" promoted by Robert Koch—discussed on the previous page—had one regrettable side effect. Microbiologists became so focused on this approach to microbiology that other, but equally important, questions about microbial life were largely ignored:
- how do microbes (e.g., bacteria) actually exist in nature?
- are they always found as free-floating cells in some liquid (i.e., in planktonic form)?
- If not, does it make a difference in understanding microorganisms—finding ways to treat those that are harmful, and developing methods for harnessing those that are beneficial—to know how they exist in nature?
They do exist in nature as individual cells, floating freely in some fluid (e.g., water or blood) in fashion similar to how they are studied in a pure culture. But it gradually became clear that microbes far more often also exist in colonies made up of lots of different microorganisms, colonies that adhere to surfaces through a slime excreted by their microscopic inhabitants.
Early Observations
In one of the earliest 20th century references to non-free floating bacteria in nature, microbiologist Arthur Henrici wrote,
It is quite evident that for the most part the water bacteria are not free floating organisms, but grow on submerged surfaces; they are of the benthos [e.g., microbes that inhabit the surface of the bottom of a lake] rather than the plancton [e.g., free floating microorganisms] (Henrici 1933).
A bit later, in Journal of Bacteriology, authors H. Heukelekian and A. Heller wrote,
Surfaces enable bacteria to develop in substrates otherwise too dilute for growth. Development takes place either as bacterial slime or colonial growth attached to surfaces. (H. Heukelekian and A. Heller 1940)
In other words, what Henrici, Heukelekian and Heller were describing were what we now call biofilms, colonies in which microbes of all sorts congregate as they attach to some surface. It is doubtful that the scientists who gave these early descriptions of biofilms actually realized what a profound difference biofilms would make to the study of microbiology.
We would like to include pictures of these pioneering scientists, but, alas, we haven't been able to locate any. Not only would such pictures be of historical interest in terms of biofilm research, but they would also be of interest with respect to of the evolving state of portraiture, as well as microbiology, over time. They would also be good for a few laughs...just as people a few years hence will laugh at our portraits when three-dimensional movie portraits, not to mention in -your-face new fashions, are the norm.
Up to the Present
More could be said (and more is said on the blue track through this section if you would like to take a gander there) about the historical investigations that have led to where we now find ourselves in the ongoing saga of biofilms. Suffice it to say at this point that as time progressed, many microbiologists began to grow uneasy with the idea that many—or even most—bacteria live as free floating spirits in a planktonic lifestyle.
We now have plenty of justification for their concern. Investigations of natural microbial habitats (Geesey et al. 1977) and human-influenced ones verify that most of the resident bacteria, often in excess of 99%, are attached as biofilms to surfaces, and that the ratio of sessile (surface-attached) to planktonic (free-floating) bacteria is often greater than 1000-10,000:1
Thus, in the late decades of the 20th century the study of biofilms began in earnest as a serious scientific endeavor. By this time scientists and engineers possessed adequate technology to effectively study microbial communities and to begin to understand the significance of biofilms.
As is true of any new field of inquiry, though, it has taken time for emerging results about biofilms to catch on amongst researchers and educators at large. One notable effort in the United States was the establishment in 1990 by the National Science Foundation of an Engineering Research Center dedicated to the study of biofilms under the direction of biofilm research pioneer William Characklis at Montana State University. Originally funded by a ten million dollar grant from the National Science Foundation, this research venture now thrives as the Center for Biofilm Engineering and is supported through individual grants obtained by Center scientists and by a number of industrial affiliates who have interest in keeping abreast of the latest advancements in biofilm research. Other similar research groups now exist in England, Germany, and other countries.
The website for the Center for Biofilm Engineering provides more information about ongoing biofilm research.
Results
Biofilm research is having quite an impact. It is now well known that microbes that are part of a biofilm exhibit different characteristics and properties than their free-floating counterparts. For example, it is more difficult to kill bad microbes that live as part of a biofilm. Thus, the study of biofilms is leading to new, more effective treatments of biofilms that lead to health problems, dental problems, and industrial problems.
Still, the study of biofilms is not well integrated into relevant curricula in microbiology, biology, environmental engineering and science, health, dentistry, and medicine. Efforts such as the one evident in this hypertextbook are helping to fix this situation. Every year, it appears, more about biofilms is being taught to college students, and the term itself is bandied about by health professionals and others with more frequency.
Biofilms are coming into the Age of Cool.
