Patterning bacteria on agar for understanding distance mediated cell to cell signaling and metabolic exchanges

Microbes, while living in close proximity in biofilms, may in other cases not be closely localized in the environment. In the latter case, their interactions and communications are dependent on myriad factors such as existence of direct connections (e.g., web of hyphae from fungi) or pools of water where they could migrate. Hence, disparate groups of microbes could subsist on nutrients in their local microhabitat while maintaining weak communication links and metabolic exchanges with groups farther afield. But, how do we probe such distance dependent communications links between groups of microbes of the same or different species in the laboratory? Using a purple pigment producing bacterium for “writing” on agar, a surface patterning technique was demonstrated to be a simple and relatively low cost tool for testing the feasibility of research ideas; for example, depositing cells in both straight and curvilinear lines on planar substrates, which may find use in understanding possible interactions between different microbial species. Although a coarse surface patterning technique compared to more refined robot assisted patterning methods, simple spread plate deposition of different microbial species, in defined patterns, on separate areas of the agar surface, constituted a useful way forward in allowing us to delve deeper into understanding microbial interactions such as those in spatially resolved synthetic microbial community. Taking into account bacterial motility patterns, pigment diffusivity, and contrast of pigment with agar background color, deposition of patterns of bacterial cells through spread plate technique is an affordable method for lending a lens to spatially defined microbial interactions for microbial brethren unable to undergo migration on the agar surface. A synopsis of the work can be found in the accompanying PDF file, while the original article, “Bacterial calligraphy: A Memento for Undergraduate Research Students”, is available in the Journal of Microbiology and Biology Education, Vol. 13, No. 2, pp. 172-174, as an open access article. URL: http://www.asmscience.org/content/journal/jmbe/10.1128/jmbe.v13i2.414