Do we need a global strategy for microbial conservation?

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Abstract

Many Kingdoms make up the three Domains of life but only two of these, the Viridiplantae and Metazoa, appear to merit the attention of conservation biologists. Given that the neglected Kingdoms, which can broadly be described as microbial, comprise by any measure (biomass or genetic diversity) the ‘unseen majority’ of life on earth [1], one might ask whether only the ‘macrobes’ are at risk of extinction or whether it is only organisms visible to the naked human eye that are worthy of conservation concern.

In this letter, I aim to highlight that the perceived ubiquity and cosmopolitanism of microbes is misplaced and that some do face threats to their continued existence. These (mostly) cryptic organisms will pose new challenges for conservation biology, which are not easily accommodated within the existing structures of the Convention on Biological Diversity (CBD); hence my proposal for a formal Global Strategy for Microbial Conservation (GSMC).

‘Macrobial’ bias in conservation biology is evident from perusal of mainstream conservation journals, where only 2% of papers relate to microbes, mostly as threats to larger organisms (notably amphibian chytridiomycosis), rather than the conservation of the threatened microbes themselves. Whereas prokaryotes barely figure in CBD documentation, Kingdom Fungi are mentioned in the updated Global Strategy for Plant Conservation: ‘Parties may choose on a national basis to include other taxa, including algae, lichens and fungi’ [2]. However, the implication of subordinate status for these organisms is clear. Given that fungi supply core ecosystem services, for example as the dominant decomposers of plant-derived lignocellulose, they are clearly of ecological importance. Thus, it is perplexing that such meagre attention and protection are afforded to them.

The most over-used phrase in microbiology, ‘everything is everywhere, the environment selects’ [3], suggests that microbial populations do not exhibit any biogeographical structure. Thus, if all microbes are geographically ubiquitous, they are unlikely to be at risk of extinction. However, even the most mobile microbial propagules, dispersed in air, vary immensely in both mass (c. 10−6–10−12 g) and tolerance of the stresses of the airborne environment, so it is inappropriate to generalise about dispersal patterns. Some microbes, for example bacteria inhabiting leaf surfaces [4], do indeed appear to be ubiquitous, but many others exhibit clear regional endemism and the absence of panmixis [5]. This is also clearly the case for many pathogens, which have (or had until humans transported them) well-defined biogeographical distributions.

The ‘game-changer’ in microbiology has been the application of rRNA barcoding and use of operational taxonomic units as species proxies. For diversity assessment and taxon circumscription, this approach allows detection of uncultured and unseen microbes, as well as usefully circumventing the lack of consensus as to the nature of any meaningful species concept for Bacteria and Archaea. High-throughput sequencing of environmental samples is now cheap, revealing not only the existence of numerous undescribed taxa and widespread cryptic speciation, but also providing increasingly detailed maps of taxon distribution [6].

Having cast doubt on the first part of the cliché, to what extent does the ‘environment select’? Notable among microbes with specific habitat requirements are the symbionts present on and inside all larger organisms, ranging from intracellular microsporidia to mycorrhizal fungi. For instance, a recently discovered anaerobic fungus, apparently specific to the hindgut of the critically endangered Somali wild ass [7], is at risk of extinction through habitat loss before it is even formally described. Equally, the loss of an obligately symbiotic microbe could increase the extinction risk of its larger host, as has been suggested for some orchids and their mycorrhizal partners [8]; in addition, changes in the microbial ecology of the mammalian digestive tract can impact on host fitness [9].

It could be argued that protecting the ecosystem will suffice to protect its microbes and this approach 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 particularly pressing example is Lake Vostok, 4 km beneath the Antarctic ice sheet, where a Russian drilling programme is within metres of the lake surface. The indigenous biota, currently unknown and possibly unique, is at risk of destruction by introduction of surface life-forms when or if the drilling resumes later this year [10].

Despite huge lacunae in knowledge of the distribution and abundance of microbial taxa, a GSMC should focus on the protection of such microbially dominated habitats. Foremost among these should be endangered soil habitats and soil types, where the most diverse microbial communities exist [11]. The thrust of activity in elevating the profile of microbial conservation via a GSMC must come from the microbiology community, but the support of the broader conservation community is also necessary for these efforts to flourish. Studies of threatened microbes need to be published in mainstream conservation journals to reach the desired audience. However, the methods used to assess their diversity or distribution are both unusual and, at present, not well established. Recognition of these facts by editors and reviewers of these journals and the appointment of microbial ecologists to their editorial boards would be great first steps.

All conservation efforts are ultimately funded by the public and here some education is needed, not only to counteract negative perceptions (‘bad bacteria’ or ‘poisonous fungi’), but also to highlight the beauty and biotechnological utility of microbes, as well as their fundamental importance to ecosystem function. As Tom Curtis [12] has stated: ‘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’.
Original languageEnglish
Pages (from-to)1-2
Number of pages2
JournalTrends in Ecology and Evolution
Volume27
Issue number1
DOIs
Publication statusPublished - 01 Jan 2012

Keywords

  • TIME
  • DIVERSITY

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