I just reread an opinion piece from Richard Moxon's group, considering whether H. influenzae produces anything that should really be called a biofilm. They agree that H. influenzae cells will grow on surfaces, but they don't think there's any real evidence that these films are the result of a developmental program that evolved because of the benefits of biofilm formation.
Although 'biofilm' can simply mean a layer of bacterial cells and biological macromolecules, associated with a solid surface or an interface, most microbiologists assume that biofilms arise by regulated developmental programs. Said another way, most microbiologists think that bacteria grow in biofilms because natural selection has favoured genes that cause them to do so. They think that bacteria respond to certain stresses that arise in biofilms, or simply to the presence of a surface, by turning on sets of genes that optimize their ability to initiate a biofilm and the physical properties of the biofilm that forms.
It's not that researchers have rigorously evaluated and discarded the alternative explanation - that biofilms form just because bacteria have adhesive organelles and macromolecules are often sticky and fibrous. But they, and grant agencies and journal editors, find the adaptive perspective more interesting, so that's what gets done and published. The Moxon paper is complaining that the term biofilm, with its aura of scientific coolness, is being applied to H. influenzae structures that fit only my simple non-adaptive definition.
Thus at least part of the reason why my simple DNA-on-glass-tubes experiment didn't work is probably that the H. influenzae cells were never going to form a biofilm at all.
After we discussed this at lab meeting, I'm going to try something different. I'll make a fake biofilm by putting a layer of top agar that contains DNA on top of normal agar plates, and then testing whether cells stick to the surface. I'll also return to an experiment I did by accident when I was a post-doc, which showed that multiple cells can bind to single DNA fragments in solution.
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3 weeks ago in Genomics, Medicine, and Pseudoscience
Bob Dylan fans are smiling.
ReplyDeleteFor Anonymous:
ReplyDeleteEarly one mornin’ the sun was shinin’,
I was layin’ in bed(field)
Wond’rin’ if she’d changed at all
If her hair was still red(field).
Her folks they said our lives together
Sure was gonna be rough
They never did like mama’s homemade dress
Papa’s bankbook wasn’t big enough.
And I was standin’ on the side of the road
Rain fallin’ on my shoes
Heading out for the east coast
Lord knows I’ve paid some dues gettin’ through,
Tangled up in goo.
Perhaps the grant will be funded and Papa's bankbook will then be big enough.
But the piece I like best is "heading out for the east coast". If one looks at the Moxon paper in PubMed and has a look for papers that cite it you find one by Izano et al. Mirob. Pathog. April '09 46(4) 207-213. This is from Jeff Kaplan's lab in Newark NJ (east coast). These authors seem to think NTHi strains are forming biofilms, and there are some interesting methods here as well.
Is Dylan ageless, or are we just old?
ReplyDeleteOnly as old as you feel. I know a couple of fairly young Dylan fans - so you needn't start planning a retirement party.
ReplyDeleteAnd only time will tell if Dylan is ageless. I've a sneaking suspicion he might be.
So what I really want to know is whether any bacteria isolated from his harmonica can form a biofilm?