Autoradiographic Study of the Localization and Evolution of Growth Zones in Bacterial Colonies

Abstract

Incorporation of [3H]leucine in the bacteria of 18 to 48 h-old colonies of Pseudomonas aeruginosa, Pseudornonas putida, Bacillus thuringiensis, Staphylococcus aureus and Escherichia coli enabled the localization of bacterial multiplication sites by means of autoradiography of sagittal sections. In colonies where fast diameter expansion occurred, all the bacteria from the peripheral corona contributed to peripheral growth; in colonies where the expansion was slower, the growth rate of the bacteria in this region was heterogeneous. Besides this peripheral growth, a central region of bacterial multiplication was always found, but with variable localization and extension. In aerobic species, such as P. aeruginosa and P. putida, the central growth site was limited to the zone of oxygen penetration into the bacterial mass. However, in facultatively anaerobic species, bacterial multiplication depended on nutrient supply. For 48 h-old colonies of S. aureus, a more complex localization of growth seemed to be affected simultaneously by nutrient penetration and accumulation of toxic substances.

Characterisation of Aerotolerant Forms of a Robust Chicken Colonizing Campylobacter coli

“…Superior resistance to peroxide stress was also noted compared to C. jejuni NCTC 11168, which had failed to grow aerobically (Rodrigues et al, 2015). Growth on solid medium creates oxygen gradients, such that facultative anaerobes have been found to be more active on the bottom layer and aerobes more rapidly dividing on the top layer of colonies (Reyrolle and Letellier, 1979). Oxygen gradients in bacterial colonies and solid media have also been measured analytically, with the top 30 μm of a gelatine medium being considered aerobic (Jeanson et al, 2015).…”

An in vivo selection method to optimize trans-splicing ribozymes

“…We hypothesized that this may be because the in vivo selection used growth on plates, whereas the doubling times were determined in liquid culture, which differ in their requirements on the cells. The difference between growth on plates and in liquid medium is caused by the diffusion of nutrients and oxygen into the bacterial colony (Reyrolle and Letelier 1979;Lewis and Wimpenny 1981), which limits the growth on plates but not in liquid culture. To test this hypothesis, we measured the growth of all clones for growth on plates containing chloramphenicol that were selected at least three times in the selection.…”

A simple mathematical model that describes the growth of the area and the number of total and viable cells in yeast colonies

“…More complex descriptions of the early development of colonies were published, mainly for bacteria (Palumbo et al . ; Reyrolle and Letellier ; Lewis and Wimpenny ; McKay and Peters ; Panikov et al . ; Theys et al .…”

“…One of the first most used and cited was that published by Pirt in 1967 for bacterial colonies, based on an initial lineal increase of the radius with time, followed by a second phase in which it is the squared radius or area which increases lineally (Cooper et al 1968;Pirt 1975). More complex descriptions of the early development of colonies were published, mainly for bacteria (Palumbo et al 1971;Reyrolle and Letellier 1979;Lewis and Wimpenny 1981;McKay and Peters 1995;Panikov et al 2002;Theys et al 2008Theys et al , 2009) but also for yeasts (Gray and Kirwan 1974;Kamath and Bungay 1988;Vulin et al 2014). Most of the works on yeasts were purely empiric, based only on colony size, without cell counting, made mainly with Saccharomyces, and using high inocula, although much lower contamination levels are actually found in natural or food environments.…”