Development of a Laboratory Model of a Phototroph-Heterotroph Mixed-Species Biofilm at the Stone/Air Interface

Abstract

Recent scientific investigations have shed light on the ecological importance and physiological complexity of subaerial biofilms (SABs) inhabiting lithic surfaces. In the field of sustainable cultural heritage (CH) preservation, mechanistic approaches aimed at investigation of the spatiotemporal patterns of interactions between the biofilm, the stone, and the atmosphere are of outstanding importance. However, these interactions have proven difficult to explore with field experiments due to the inaccessibility of samples, the complexity of the ecosystem under investigation and the temporal resolution of the experiments. To overcome these limitations, we aimed at developing a unifying methodology to reproduce a fast-growing, phototroph-heterotroph mixed species biofilm at the stone/air interface. Our experiments underscore the ability of the dual-species SAB model to capture functional traits characteristic of biofilms inhabiting lithic substrate such as: (i) microcolonies of aggregated bacteria; (ii) network like structure following surface topography; (iii) cooperation between phototrophs and heterotrophs and cross feeding processes; (iv) ability to change the chemical parameters that characterize the microhabitats; (v) survival under desiccation and (vi) biocide tolerance. With its advantages in control, replication, range of different experimental scenarios and matches with the real ecosystem, the developed model system is a powerful tool to advance our mechanistic understanding of the stone-biofilm-atmosphere interplay in different environments.

Byproduct Cross Feeding and Community Stability in an In Silico Biofilm Model of the Gut Microbiome

“…Natural microbial communities have evolved numerous mechanisms for ensuring species coexistence, most notably the biofilm mode of growth. Spatial metabolite gradients within biofilms can allow otherwise slower growing species to establish metabolic niches favorable for their growth [21][22][23][24]. Cross feeding of secreted metabolic byproducts is another mechanism used by microbial communities to enhance the competitiveness of slower growing species and achieve community stability [17][18][19][20].…”

“…These cross-feeding relationships are a result of metabolic specialization and establish a food web within the community that maximizes utilization of available resources. When combined with the biofilm mode of growth and associated diffusional limitations, cross feeding establishes local metabolic niches that allow otherwise slower growing species to coexist with faster growing species and is hypothesized to stabilize the community against environmental perturbations [21][22][23][24]. The spatial partitioning of metabolism and physical immobilization by secreted polymers make biofilm cultures distinct from planktonic cultures grown in well-mixed environments where coexistence is not possible unless the species have the same growth rate.…”

Fungi and Bacteria in Indoor Cultural Heritage Environments: Microbial-related Risks for Artworks and Human Health

“…Biofilm micro-fragments from Saint Cave were analysed by CLSM (Olympus FV 300 -Argon, 488.0nm, He-Ne, 543.5nm), exploiting their self-fluorescence property [36].…”

Photorespiration and Rate Synchronization in a Phototroph-Heterotroph Microbial Consortium

“…We consider here stability of steady states of the chemostat system, beginning with the single species community model (28)- (31), which has two possible steady states, namely washout (P 1 (t) = 0) and viable (P 1 …”

“…It is not immediately clear why this should be the case, as competition for resources, e.g., space or nutrients, is possible, and it seems that oxygenic phototrophs might be expected to be able to outcompete heterotrophic neighbors for those resources. Even so, multispecies communities are observed including in environments where heterotrophs might not be able to persist on their own [1]. Further, there are at least some examples of communities where resident phototrophs lack critical anabolic capabilities and must instead rely on nearby organisms to supply them [2].…”