Community proteomics applied to natural microbial biofilms resolves how the physiology of different populations from a model ecosystem change with measured environmental factors in situ.The initial colonists, Leptospirillum Group II bacteria, persist throughout ecological succession and dominate all communities, a pattern that resembles community assembly patterns in some macroecological systems.Interspecies interactions, and not abiotic environmental factors, demonstrate the strongest correlation to physiological changes of Leptospirillum Group II.Environmental niches of subdominant populations seem to be determined by combinations of specific sets of abiotic environmental factors.
A fundamental question in microbial ecology addresses how organisms regulate their metabolic activities within natural communities as environmental constraints and population structures change. Recent advances in molecular biology have allowed for investigation into the physiology of organisms within natural settings, opening the door to understanding microbial metabolic responses in situ. Here, we have examined how a diverse set of organisms from microbial biofilms alters their protein complements as environmental parameters change and as ecological succession occurs. We find that, when growing in newly formed biofilms, the dominant organism within these communities exhibits a metabolism focused on rapid growth, protein synthesis, and stress defense. As community succession proceeds and secondary colonizers populate maturing biofilms, this organism's metabolism switches to one focused on synthesizing many essential cellular components, including amino acids, DNA, and carbohydrates. We also find that the metabolism of this organism is not strongly influenced by external environmental factors over the range of conditions studied. In addition, the protein complements of secondary colonizers seem to be highly responsive to changes in specific environmental parameters (e.g. pH, conductivity, temperature), which may limit their distribution across this environment. These findings provide insight into which of these environmental factors may drive community assembly in a natural microbial assemblage, and, in turn, may influence the metabolism of individual populations.
An important challenge in microbial ecology is developing methods that simultaneously examine the physiology of organisms at the molecular level and their ecosystem level interactions in complex natural systems. We integrated extensive proteomic, geochemical, and biological information from 28 microbial communities collected from an acid mine drainage environment and representing a range of biofilm development stages and geochemical conditions to evaluate how the physiologies of the dominant and less abundant organisms change along environmental gradients. The initial colonist dominates across all environments, but its proteome changes between two stable states as communities diversify, implying that interspecies interactions affect this organism's metabolism. Its overall physiology is robust to abiotic environmental factors, but strong correlations exist between these factors and certain subsets of proteins, possibly accounting for its wide environmental distribution. Lower abundance populations are patchier in their distribution, and proteomic data indicate that their environmental niches may be constrained by specific sets of abiotic environmental factors. This research establishes an effective strategy to investigate ecological relationships between microbial physiology and the environment for whole communities in situ.