COOPERATIVE ORGANIZATION OF BACTERIAL COLONIES: From Genotype to Morphotype

Abstract

In nature, bacteria must often cope with difficult environmental conditions. To do so they have developed sophisticated cooperative behavior and intricate communication pathways. Utilizing these elements, motile microbial colonies frequently develop complex patterns in response to adverse growth conditions on hard surfaces under conditions of energy limitation. We employ the term morphotype to refer to specific properties of colonial development. The morphologies we discuss include a tip-splitting (T) morphotype, chiral (C) morphotype, and vortex (V) morphotype. A generic modeling approach was developed by combining a detailed study of the cellular behavior and dynamics during colonial development and invoking concepts derived from the study of pattern formation in nonliving systems. Analysis of patterning behavior of the models suggests bacterial processes whereby communication leads to self-organization by using cooperative cellular interactions. New features emerging from the model include various models of cell-cell signaling, such as long-range chemorepulsion, short-range chemoattraction, and, in the case of the V morphotype, rotational chemotaxis. In this regard, pattern formation in microorganisms can be viewed as the result of the exchange of information between the micro-level (the individual cells) and the macro-level (the colony).

Deadly competition between sibling bacterial colonies

“…Experiments for a higher concentration of the gel extract (Fig. 4C) revealed an even more striking transition from the branching morphology of the P. dendritiformis to the chiral one (7,11), as is shown in Fig. 1B.…”

“…We used a spore-forming Gram-positive motile bacterial strain, Paenibacillus dendritiformis (T morphotype) (7). Each bacterium is rod-shaped with dimensions Ϸ4 ϫ 1 m (7, 11).…”

“…Each bacterium is rod-shaped with dimensions Ϸ4 ϫ 1 m (7, 11). The bacteria secrete lubricating substances (such as surfactin), and they move in this thin lubricant layer on top of a substrate such as a high-concentration agar gel (7,11). The morphology of the patterns and the dynamics of the growth are sensitive to the nutrient level, substrate hardness, temperature, and humidity (7,11).…”

“…When exposed to harsh environmental conditions such as starvation, hard surfaces, extreme heat, and hazardous chemicals, the bacteria can collectively develop sophisticated strategies for adaptation and survival. One aspect of this cooperative behavior is the formation of complex colonies with different spatiotemporal patterns, as needed for efficient response to the environmental conditions (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13).…”

O pensamento epidemiológico evolutivo sobre as infecções

“…Em outras palavras, quanto maior a adversidade mais aquela é necessária. Como exemplo, podem-se mencionar as observações sobre a organização 2 Entende-se por coerência parasitária a obtenção de informações necessárias à expressão genética, ao crescimento e à diferenciação. Tais interconexões quimiotácticas constituem verdadeiras redes cujo funcionamento é indispensável àquelas finalidades, implicando respostas às solicitações externas.…”