Pronounced Effect of the Nature of the Inoculum on Biofilm Development in Flow Systems

Abstract

Biofilm formation renders sessile microbial populations growing in continuous-flow systems less susceptible to variation in dilution rate than planktonic cells, where dilution rates exceeding an organism's maximum growth rate ( max ) results in planktonic cell washout. In biofilm-dominated systems, the biofilm's overall max may therefore be more relevant than the organism's max , where the biofilm max is considered as a net process dependent on the adsorption rate, growth rate, and removal rate of cells within the biofilm. Together with lag (acclimation) time, the biofilm's overall max is important wherever biofilm growth is a dominant form, from clinical settings, where the aim is to prevent transition from lag to exponential growth, to industrial bioreactors, where the aim is to shorten the lag and rapidly reach maximum activity. The purpose of this study was to measure CO 2 production as an indicator of biofilm activity to determine the effect of nutrient type and concentration and of the origin of the inoculum on the length of the lag phase, biofilm max , and steady-state metabolic activity of Pseudomonas aeruginosa PA01 (containing gfp), Pseudomonas fluorescens CT07 (containing gfp), and a mixed community. As expected, for different microorganisms the lengths of the lag phase in biofilm development and the biofilm max values differ, whereas different nutrient concentrations result in differences in the lengths of lag phase and steady-state values but not in biofilm max rates. The data further showed that inocula from different phenotypic origins give rise to lag time of different lengths and that this influence persists for a number of generations after inoculation.Microbial growth in batch cultures has been studied for a long time, and the observed phases have been designated the lag phase, the acceleration phase, the exponential phase, the retardation phase, the stationary phase, and the phase of decline although not each culture displays all of the mentioned phases (16). In contrast to batch cultures and static (no flow) biofilms (e.g., those that form in 96-well plates), the increase in biofilm cells in a flowing environment is a net process that is dependent on the irreversible adsorption rate of cells to the surface, the growth rate of the microorganisms, and the removal rate of cells lost to the bulk flow (18). There are numerous benefits for the cells in biofilms, e.g., protection against antimicrobials and the opportunity for and proliferation by continuous cell dispersion. There is also a possible competitive advantage if cells colonize surfaces at multiple sites and grow in such a manner that the resulting three-dimensional architecture exposes the maximum biofilm surface area to surrounding nutrients. The most successful colonizers would therefore be the cells with the ability to adhere to the surface (and stay adhered) and to start multiplying at maximum rate. The process of events from being free-floating cells to the so-called permanently surface-attached phase involves early steps including ...

Characterization of thermophilic bacilli from a milk powder processing plant

“…It has also been shown that the lag phase decreases when cells from a biofilm are used for inoculating for formation of a biofilm compared with those growing planktonically in the bulk fluid (Kroukamp et al . ). This was important so that strains used in the biofilm assay were primed for biofilm formation.…”

Detachment characteristics of a mixed culture biofilm using particle size analysis

“…Previous studies have shown that detachment occurs throughout biofilm development and it is incorrect to assume that detachment occurs only after the biofilm has matured [16,17]. This suggests that that biofilm formation is a mechanism for proliferation in addition to the role in survival typically mentioned in the literature [18]. The objective of this article was to study biofilm reproducibility in steady-state mixedculture biofilm operation with a particular emphasis on detachment rate.…”

Exploring the relationship between exposure to technological and gastrointestinal stress and probiotic functional properties of lactobacilli and bifidobacteria

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