A third mode of surface‐associated growth: immobilization of <i>Salmonella enterica</i> serovar Typhimurium modulates the RpoS‐directed transcriptional programme

Knudsen, Gitte M.; Nielsen, Maj-Britt; Grassby, Terri; Danino-Appleton, Vittoria; Thomsen, Line Elnif; Colquhoun, Ian J.; Brocklehurst, T.F.; Olsen, John Elmerdahl; Hinton, Jay C. D.

doi:10.1111/j.1462-2920.2012.02703.x

Cited by 27 publications

(24 citation statements)

References 89 publications

(165 reference statements)

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Section: Lag Phasecontrasting

confidence: 85%

“…This observation is in contrast with the results published by Knudsen et al (2012), where for S. Typhimurium grown at 25°C in gel cassettes, the lag phase for colonies is significantly longer than the one for planktonic cells. Differences between Knudsen et al (2012) and the present work can probably be accounted to the use of different experimental set-ups. As stated in this study, Boons et al (2013) observed similar lag phase durations in both liquid systems and different gelled systems for S. Typhimurium and E. coli at 23.5°C at low salt concentrations.…”

Section: Lag Phasecontrasting

confidence: 85%

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Effect of cell immobilization on the growth dynamics of Salmonella Typhimurium and Escherichia coli at suboptimal temperatures

Smet

Derlinden

Mertens

et al. 2015

International Journal of Food Microbiology

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Predictive microbiology has recently acknowledged the impact of the solid(like) food structure on microbial behavior. The presence of this solid(like) structure causes microorganisms to grow as colonies and no longer planktonically as in liquid. In this paper, the growth dynamics of Salmonella Typhimurium and Escherichia coli were studied as a function of temperature, considering different growth morphologies, i.e., (i) planktonic cells, (ii) immersed colonies and (iii) surface colonies. For all three growth morphologies, both microorganisms were grown in petri dishes. While E. coli was grown under optimal pH and water activity (aw), for S. Typhimurium pH and aw were adapted to 5.5 and 0.990. In order to mimic a solid(like) environment, 5% (w/v) gelatin was added. All petri dishes were incubated under static conditions at temperatures in the range [8.0°C-22.0°C]. Cell density was determined via viable plate counting. This work demonstrates that the growth morphology (planktonic vs. colony) has a negligible effect on the growth dynamics as a function of temperature. The observation of almost equal growth rates for planktonic cultures and colonies is in contrast to literature where, mostly, a difference is observed, i.e., μplanktonic cells≥μimmersed colonies≥μsurface colonies. This difference might be due to shaking of the liquid culture in these studies, which results in a nutrient and oxygen rich environment, in contrast to the diffusion-limited gel system. Experiments also indicate that lag phases for solid(like) systems are similar to those for the planktonic cultures, as can be found in literature for similar growth conditions. Considering the maximum cell density, no clear trend was deducted for either of the microorganisms. This study indicates that the growth parameters in the suboptimal temperature range do not depend on the growth morphology. For the considered experimental conditions, models previously developed for liquid environments can be used for solid(like) systems.

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Section: Lag Phasecontrasting

confidence: 85%

Section: Lag Phasecontrasting

confidence: 85%

Effect of cell immobilization on the growth dynamics of Salmonella Typhimurium and Escherichia coli at suboptimal temperatures

Smet

Derlinden

Mertens

et al. 2015

International Journal of Food Microbiology

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“…Exceptionally, lag duration of cells growing on a gel surface was found longer than in planktonic growth at 25°C (Knudsen et al, 2012). Variation in composition among the used model systems in other studies and in this study could be the key for the existence or not of differences at the lag phase between planktonic and surface growth.…”

Section: Accepted Manuscriptmentioning

confidence: 76%

Influence of food intrinsic complexity on Listeria monocytogenes growth in/on vacuum-packed model systems at suboptimal temperatures

Baka

Noriega

Langendonck

et al. 2016

International Journal of Food Microbiology

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Food intrinsic factors e.g., food (micro)structure, compositional and physicochemical aspects, which are mutually dependent, influence microbial growth. While the effect of composition and physicochemical properties on microbial growth has been thoroughly assessed and characterised, the role of food (micro)structure still remains unravelled. Most studies on food (micro)structure focus on comparing planktonic growth in liquid (microbiological) media with colonial growth in/on solid-like systems or on real food surfaces. However, foods are not only liquids or solids; they can also be emulsions or gelled emulsions and have complex compositions. In this study, Listeria monocytogenes growth was studied on the whole spectrum of (micro)structure, in terms of food (model) systems. The model systems varied not only in (micro)structure, which was the target of the study, but also in compositional and physicochemical characteristics, which was an inevitable consequence of the (micro)structural variability. The compositional and physicochemical differences were mainly due to the presence or absence of fat and gelling agents. The targeted (micro)structures were: i) liquids, ii) aqueous gels, iii) emulsions and iv) gelled emulsions. Furthermore, the microbial dynamics were studied and compared in/on all these model systems, as well as on a compositionally predefined canned meat, developed in order to have equal compositional level to the gelled emulsion model system and represent a real food system. Frankfurter sausages were the targeted real foods, selected as a case study, to which the canned meat had similar compositional characteristics. All systems were vacuum packed and incubated at 4, 8 and 12°C. The most appropriate protocol for the preparation of the model systems was developed. The pH, water activity and resistance to penetration of the model systems were characterised. Results indicated that low temperature contributes to growth variations among the model systems. Additionally, the firmer the solid system, the faster L. monocytogenes grew on it. Finally, it was found that L. monocytogenes grows faster on canned meat and real Frankfurters, as found in a previous study, followed by liquids, aqueous gels, emulsions and gelled emulsions. This observation indicates that all model systems, developed in this study, underestimated L. monocytogenes growth. Despite some limitations, model systems are overall advantageous and therefore, their validation is always recommended prior to further use.

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“…Bacterial biofilms have been intensively studied because they adversely affect humans in medical and industrial settings (for reviews, see references 7, 8, and 9). Throughout the history of microbiology, bacterial colonies have been used for diagnostic and enumerative ends but have rarely been objects of scientific scrutiny for their own sake (10)(11)(12)(13)(14)(15). However, the available data show that there are many similarities between biofilms and colonies.…”

mentioning

confidence: 99%

Massive Diversification in Aging Colonies of Escherichia coli

et al. 2014

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The evolutionary success of bacteria depends greatly on their capacity to continually generate phenotypic diversity. Structured environments are particularly favorable for diversification because of attenuated clonal interference, which renders selective sweeps nearly impossible and enhances opportunities for adaptive radiation. We examined at the microscale level the emergence and the spatial and temporal dynamics of phenotypic diversity and their underlying causes in Escherichia coli colonies. An important dynamic heterogeneity in the growth, metabolic activity, morphology, gene expression patterns, stress response induction, and death patterns among cells within colonies was observed. Genetic analysis indicated that the phenotypic variation resulted mostly from mutations and that indole production, oxidative stress, and the RpoS-regulated general stress response played an important role in the generation of diversity. We observed the emergence and persistence of phenotypic variants within single colonies that exhibited variable fitness compared to the parental strain. Some variants showed improved capacity to produce biofilms, whereas others were able to use different nutrients or to tolerate antibiotics or oxidative stress. Taken together, our data show that bacterial colonies provide an ecological opportunity for the generation and maintenance of vast phenotypic diversity, which may increase the probability of population survival in unpredictable environments.

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A third mode of surface‐associated growth: immobilization of Salmonella enterica serovar Typhimurium modulates the RpoS‐directed transcriptional programme

Cited by 27 publications

References 89 publications

Effect of cell immobilization on the growth dynamics of Salmonella Typhimurium and Escherichia coli at suboptimal temperatures

Effect of cell immobilization on the growth dynamics of Salmonella Typhimurium and Escherichia coli at suboptimal temperatures

Influence of food intrinsic complexity on Listeria monocytogenes growth in/on vacuum-packed model systems at suboptimal temperatures

Massive Diversification in Aging Colonies of Escherichia coli

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