I f i condesed say all the bacteria from the average desk into a single particle would it be visable to the naked eye? ie perhaps the size of a grain of sand or pin head etc? Do the bacteria then if this is the case actually reside on say a desk surface at low densities relative to their size despite their huge numbers? For instance very very roughly perhps only .5 of or 1-2-3 percent of any given desk surfsace is actually covered collectivly in bacteria hence the reason you see the desk so clearly and not the bacteria at all. Due to their small size and relatively low density?
I think the short answer is that it depends on how 'clean' the desk is.
I can't comment on the percentage of an average desk bacteria cover.
And yes bacteria can colonise surfaces at low numbers and low densities. The best example is our skin which carries loads of bacteria on its surface, none of which is visible to the naked eye.
I can’t vouch for the numbers, and obviously some desks will be cleaner than others, but one ‘study’ (http://articles.cnn.com/2004-12-13/heal =PM:HEALTH and http://news.bbc.co.uk/1/hi/health/3505414.stm) in 2002 claimed there were approx. 21,000 bugs per square inch on a desktop compared to 49 bugs per square inch on toilet seats. That was equated to 10 million bugs on a desktop (must be a fairly small desk!). The commentaries on these articles don’t indicate what sort of microbes, or how they got there (e.g., coughing) etc.
There are probably over a million bacteria in a visible, say 1mm colony that will be growing at >1 cell deep (at least one that is growing on growth medium under optimal conditions so doubling about every 20-30 minutes). So you wouldn’t see a colony, but if you condensed the 10 million you’d maybe have 10 small colonies covering an area of about 30 square mm over 476 square inches (approx 310,000 square mm) = around 0.0097% coverage.
Last edited by Steve Lolait (24th Oct 2011 13:53:18)
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