Biological Soil Crusts
Our group has made great efforts to develop methods to probe cyanobacterial metabolism. Recently, we have extended this work to study cyanobacterial communities in Biological soil crusts in collaboration with Ferran Garcia-Pichel, Cheryl Kerfeld, Eoin Brodie, and Andrila Mukhopadhyay as part of a LBNL funded LDRD program.
Biological soil crusts (BSC; see Belnap and Lange, 2001; Garcia-Pichel, 2002) are complex topsoil microbial communities recently recognized to be locally important agents of C cycling in arid lands, and globally relevant. Their cryptic nature and their mode of operation, based on slow growth/high resilience and pulsed activity under extreme conditions, together with a short history as a scientific subject, have contributed to our present lack of understanding regarding their function. BSCs are initiated by growth of pioneer cyanobacteria during episodic events of available moisture, with the subsequent entrapment of mineral particles by a network of cyanobacterial filaments and a matrix of extracellular slime. Eventual undisturbed development will lead to complex multi-species assemblages that harbor important bacterial, archaeal, fungal, algal, even lichenic and moss populations (Nagy et al, 2005; Soule et al, 2009; Bates and Garcia-Pichel, 2009). Because arid lands make a sizeable proportion of all continents, the global standing C stock in BSCs probably exceeds 1014 g C (Garcia-Pichel et al., 2002), making soil crusts arguably the most extensive biosynthetic biofilm on the planet.
Their metabolic activities, when wet, are large enough to contribute a significant proportion of the local biogeochemical cycling of C and nitrogen (N) in arid lands (Lange and Belnap, 2001; Johnson and Garcia-Pichel, 2006). The scale and potential sensitivity of these crusts to temperature and wetting frequency/duration make them particularly relevant to understanding climate change. Additionally, these crusts effectively bind arid soil together preventing dust clouds from forming. The potential collapse of these crusts could resulting in dust formation may have significant impact on climate change [Kaufman 2005] and the environment [taylor 2002].
Solving such apparent paradoxes and understanding how the particular lifestyle of crusts constrains their biology, making it inherently different from that of temperate soil microbes, will not be possible if we treat them as black boxes. We need to understand how (micro)biology works under these extreme conditions of short pulsed activity and long periods of quiescence. We are collaborating with Ferran Garcia-Pichel, Cheryl Kerfeld, Eoin Brodie, and Andrila Mukhopadhyay to integrate genomic, transcriptomic, and metabolomic methods to undertand this important microbial community.
When coupled to explicit mapping of activities to particular microniche compartments or particular microbial actors, these approaches stand to provide the first opportunities to comprehensively understand the biogeochemical potential of these communities and to predict their continued contribution to the global C cycle or their future responses to global change.
This video shows the movement of the dominant cyanobacteria, Microcoleus vaginatus migrating to the surface and producing oxygen upon wetting
For more information on desert biological soil crusts see: