Stand Up For the Little Guys
Let's start thinking on how to save the Earth's endangered microbes.
Photograph by iStockphoto/Thinkstock.
"If the last blue whale choked to death on the last panda, it would be disastrous but not the end of the world. But if we accidentally poisoned the last two species of ammonia oxidizers, that would be another matter. It could be happening now and we wouldn't even know."
The words of environmental engineer Tom Curtis sum up the seeming disregard for microbial life beautifully. The tree of life is diverse. Many kingdoms make up its three domains, but only two of those kingdoms within the domain Eukaryota, the Plantae and Animalia, appear to merit conservation biologists' attention.
The neglected kingdoms are broadly microbial, and by any measure, be it their biomass or genetic diversity, they comprise the "unseen majority" of life. Are only "macrobes" at risk of extinction? Are only those organisms visible to the naked eye worthy of conservation?
No. Microbes may appear endlessly abundant, everywhere and to an extent interchangeable, but some do face real threats to their existence. The problem is that microbes, for reasons including a lack of descriptive data, are not easily accommodated within the 1993 Convention on Biological Diversity (CBD). That's why I propose a formal Global Strategy for Microbial Conservation.
You only have to look at mainstream conservation journals to see the macrobial bias: Only 2 percent of papers relate to microbes, and even then mostly as threats to larger organisms rather than organisms that must themselves be preserved.
Whereas the chiefly single-celled prokaryotes barely figure in the CBD, fungi at least get a mention in the updated Global Strategy for Plant Conservation, which is part of the convention: "Parties may choose on a national basis to include other taxa, including algae, lichens and fungi." The implication of subordinate status is clear, even though fungi are the dominant decomposers of plant-derived lignocellulose, the major structural component of all plants, and release nutrients from dead material to the soil, vital for agriculture. Given that fungi supply core ecological functions that are beneficial to humankind, it is perplexing that they are afforded such meager attention and protection.
There is a much overused phrase in microbiology—everything is everywhere, but the environment selects—which suggests that microbial populations are not localized but geographically ubiquitous, and unlikely to be at risk. Some, such as bacteria on leaf surfaces, do appear to be ubiquitous, but many others are not. This is also the case for many pathogens of humans, animals or crops, which have, or had until humans transported them, well-defined distributions. So habitat change in a limited area may threaten them.
The symbiotic microbes present on and inside all larger organisms are notable among those that need specific habitats. A recently discovered anaerobic fungus that is apparently specific to the hindgut of the critically endangered Somali wild ass, for example, is at risk of extinction through habitat loss before it is even formally described. This could also work in reverse—the loss of some symbiotic microbes could increase the extinction risk of their hosts given their mutual interdependence, as has been suggested for some orchids and their mycorrhizal partners. In addition, changes in the microbial ecology of the mammalian digestive tract can harm the health of the host.
Central to our improved understanding of all this is DNA bar-coding, which allows the detection of uncultured and unseen microbes. High-throughput sequencing of environmental samples is now cheap. This is revealing many undescribed taxa and extensive cryptic speciation—groups of microbes that look very similar but are distinct species. Importantly, it is also providing detailed maps of distribution.
It could be argued that protecting the ecosystem will suffice to protect its microbes. This is clearly sensible when resources are scarce. However, many ecosystems are neglected in conservation strategies simply because of the absence of larger organisms, for instance desert soil crusts, glaciers, or unusual geological formations.
One topical example is Lake Vostok, 4 kilometers beneath the Antarctic ice, where a Russian drilling program recently reported breaching the lake surface. The indigenous biota, currently unknown and possibly unique, is at risk of destruction by the introduction of surface life forms. The potential exploration of other deep sea or subsurface ecosystems will raise other "Schrödinger's cat" dilemmas.
Despite huge gaps in our knowledge of the distribution and abundance of microbes, a global strategy should focus on the protection of such microbially dominated habitats. It should include, as a matter of priority, endangered soil habitats and soil types, where the most diverse microbial communities are to be found.
Raising the profile of microbial conservation must come from microbiologists, but the support of the broader conservation movement is needed. Studies of threatened microbes need to be published in mainstream conservation journals. The appointment of microbial ecologists to editorial boards would help.
Finally, all conservation efforts are ultimately funded by the public and here education is needed to counteract negative perceptions, such as that all bacteria are "bad" or all fungi are "poisonous." It should also highlight the beauty and biotechnological usefulness of microbes, as well as their fundamental importance to the wider living world.
This article originally appeared in New Scientist.
Gareth Griffith is a microbial ecologist at Aberystwyth University in the U.K. This article is based on his letter in the journal Trends in Ecology and Conservation.