Decho Lab Research Interests:
- microbial mats
- extracellular polymeric secretions (EPS) of bacteria
- chemical communication under natural conditions
- biofilms in infections, pathogen survival, antibiotic interactions
- nanoparticles as antimicrobial delivery vehicles for infections
- nanoparticle environmental interactions in biofilms
Bacteria are pivotal components in both natural and engineered systems. ‘Biofilms’ are the ‘extracellular bastions of bacteria’, and consist of microbial cells embedded within a protective matrix of extracellular polymeric secretions (EPS) (Figure 1). Many biofilms are now known to exhibit a high level of organization, physical microarchitecture, and extracellular communication networks. This allows different bacteria to organize themselves and coordinate some activities- acting as a ‘single group.”
When bacteria take this form, they become a fundamental link between the ‘environment and human health’. Biofilms are involved in human: dental plaque on teeth, urinary-tract infections (UTIs), and other polymicrobial infections. They are responsible for greater than 70% of hospital-acquired (nosocomial) infections, and result in multi-billion $$ costs to society, health and industry. Biofilms also serve many important and beneficial roles in lining our intestines/colon and upper respiratory track. In natural environments, such as oceans, biofilms are virtually everywhere, contributing to marine snow formation in the water-column, omnipresent microscopic sediment coatings, and contribute strongly to global carbon cycling processes.
Figure 1. Bacteria form a biofilm in several steps: (1) planktonic (individual) bacteria attach to surface; (2) surround themselves with secreted extracellular polymers (EPS); (3) chemical communication occurs between/among cells and results in altered gene expression; and (4) coordinate activities. The net result is a community that is orders of magnitude more resilient and adaptable than individual planktonic cells.
In ocean systems, biofilms form microscopic coatings on virtually all surfaces. Further, they influence marine snow formation, organic matter cycling, larval settlement processes, sediment stability, and the optical properties of sediments. From an environmental standpoint, biofilms are ‘sorptive sponges’ and important sites for the binding, transformation and trophic-transfer of contaminants (and potentially toxic nanoparticles). In health settings, the biofilm represents a ‘resistant refugia’ for pathogenic (disease-causing) bacteria. Biofilms are responsible for greater than 70% of hospital-acquired (nosocomial) infections, drinking water related outbreaks of disease, and may even play roles in the initial events of certain cancers. This results in a multi-billion $$ cost to society, health and industry.
Many biofilms are now known to exhibit a high level of organization, physical microarchitecture, and extracellular chemical communication networks. This allows bacterial cells in proximity, to act as a ‘single group’, and further, allows different microbial groups within a biofilm to coordinate activities; providing greater metabolic efficiency and resiliency than would be otherwise possible. Thus, chemical communication within biofilms likely contributes to the 1) high-diversity, 2) adaptability and 3) resiliency of bacteria in both natural systems and hospital-disease settings.
My research interests center on the role of the ‘extracellular matrix’ of bacterial ‘biofilms’ in marine, environmental and health-related processes. We are exploring a range of biological and chemical processes that occur within biofilms in order to understand how they function, and ultimately, how they may be manipulated or controlled. Our laboratory is probing the microspatial organization of communities, physical chemical microarchitecture of EPS, and chemical communication networks of biofilms. We are using molecular investigations, nanochemistry, and spectroscopic and imaging approaches to investigate biofilms in situ and under laboratory conditions. We utilize confocal (CSLM) and multi-photon (MP-SLM) scanning laser microscopy, environmental scanning (ESEM) and transmission (TEM) electron microscopy, atomic force microscopy (AFM), NMR, FT-IR and Raman spectroscopy in order to probe the extracellular matrix of biofilms. Finally, a rapidly-emerging area of interest centers on the interactions of nanoparticles in biofilms for the purposes of probing and manipulating biofilms, and for understanding the environmental effects of nanoparticles.
Figure 2. In human-health settings, the biofilm forms a
‘resistant refugia’ for pathogenic (disease-causing) bacteria
against antimicrobial agents. A few examples include their roles in
persistent (polymicrobial), urinary-tract (UTIs), hospital-acquired
(nosocomial) infections; dental plaque formation; and drinking-water
related outbreaks of disease. Biofilms may even play roles in the
initial events of certain cancers. In natural environments, biofilms
act as efficient ‘sorptive sponges’ for the binding trophic-transfer
of contaminants, and colloids, even ‘nanoparticles’. In marine
systems, biofilms and their EPS influence the formation of ‘marine
snow’ in the water column, global carbon cycling, larval settlement
processes, and the physical stability and optical properties of
|Surface of marine sediments from an intertidal mudflat, imaged in a hydrated state using cold-stage SEM.||Confocal (CSLM) image of a stromatolite biofilm community. (carbonate sand grains BLUE, EPS are GREEN, cyanobacteria are RED.)||Individual EPS molecules (alginate) imaged using atomic-force microscopy|