A bugs life?

September 22, 2008 6:42 AM

Help me settle a bet about the total number of identified bacteria and viruses.

Last week a friend, recalling a university lecture, said that the number of named and identified species of bacteria and viruses account for 98% of the total number of named species. I doubted this and thought it more likely that though there are fifty times as many species of bacteria and virus as there are any other kind of species, not all them have yet been named and catalogued. I suggested that this 98% figure is more of an estimate.
I base this supposition on the fact that it's so much easier to identify species that are visible to the naked eye and that people have had a lot longer to do it (the microscope being a relatively recent invention). Am I wrong?
Google has failed me, can Metafilter help?

P.S. As part of my searching I’ve been unable to find an estimate of the total number of identified species, and this has rather piqued my interest. Any help with this would be great too.

Thanks!

posted by greytape to science & nature (8 comments total)

Maybe I'm confused, but isn't 2% also 1/50? Therefore, there are 50 times more bacteria and viruses by both estimates? I have no idea either way, but I assume you are including anything invisible to the naked eye.
posted by Brian B. at 7:04 AM on September 22, 2008

I think it's bogus. It may well be possible that there are that many bacterial species, but by no means are they more than a small percentage of identified species.

Number of species suggest that at best we have 1.5 to 2 million species that have been identified, with estimates of the total number on earth ranging as high as 100 million(or more).

It is well known and accepted that over half of all described species are insects, which is where your pal may have gotten the (bug? or germ? of an) idea. But "little continues to be known about the distribution and biology of vast numbers of species groups, including arthropods, fungi, and nematodes." I would suggest this applies to bacteria as well. We know the medically important ones, but since even the human elbow has six "tribes" of bacteria piggybacking along, which we're only beginning to study, I would imagine the number of uniedtified bacteria species to be enormous.
posted by dhartung at 7:05 AM on September 22, 2008

Craig Venter found a lot of stuff in the ocean. There should be some numbers buried in that article.
posted by b1tr0t at 7:20 AM on September 22, 2008

Perhaps I haven't made myself very clear.

Maybe I'm confused, but isn't 2% also 1/50? Therefore, there are 50 times more bacteria and viruses by both estimates?

I'm quite willing to concede that there are fifty times as many bateria/viruses as anything else (I have no idea). What I don't believe is that have all been catalogued and named. The first answers here seem to be bearing that out.
posted by greytape at 7:43 AM on September 22, 2008

Most bacteria species haven't been named. Only about 10,000 species have been named and it is certain that there are many many many times that number really. There have been a number of articles about this, for example in Science[pdf at Scribd].

Quote from the article "There are more than 10^16 prokaryotes in a ton of soil compared to a mere 10^11 stars in our galaxy. Astronomers have wisely inferred the population of celestial objects by mathematical inference. Now microbiologists are following suit, adopting a similar strategy to estimate the number of prokaryote taxa in soil. As shown by Gans et al. on page 1387 (1), the inferred diversity is staggering--higher than previously thought by almost three orders of magnitude."

And, since there have been about 2 million species named (according to the Millenium Ecosystem Assessment), it is safe to say that named bacteria species account for only a small proportion of the total number of named species.

Of the named species, most are insects (there's a graph here).

If we're talking all species (both named and unnamed) then I'd place my money on there being oodles more bacteria species than other kinds of species. However, it's worth noting that the species concept for bacteria is pretty flaky at the moment. This is mainly because their most of their reproduction is asexual rather than sexual, they don't have easily definable morphological features and because there's an immense amount of diversity out there. Put simply, "species" for bateria means something different than "species" for animals like mammals/insects.
posted by jonesor at 7:43 AM on September 22, 2008

the number of named and identified species of bacteria and viruses account for 98% of the total number of named species.

I think you're misinterpreting what this sentence means. It means that, if you add up all of the named species of things, bacteria and viruses account for 98% of those. So, with respect to the validity of this claim, unnamed species of things are completely irrelevant.


What I don't believe is that have all been catalogued and named.

Based on what you've written here, that's not what's being claimed.
posted by toomuchpete at 8:02 AM on September 22, 2008

Also - it is difficult to rigorously define what the term 'species' even means for organisms which don't reproduce sexually.
posted by kickingtheground at 8:53 AM on September 22, 2008

Yeah, it's difficult enough to figure out where one species starts and another ends even for organisms which do reproduce sexually. I just mention this because I find ring species really cool.
posted by Solon and Thanks at 11:28 AM on September 22, 2008