Browsing by Author "Pant K"

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Conditional synergy: Impact of nutrient abundance on multispecies biofilm formation and sanitizer tolerance
(Elsevier Ltd, 2026-03-01) Pant K; Palmer J; Flint S
Bacteria exist in varying nutrient conditions and complex microbial consortia. Pseudomonas fluorescens, Staphylococcus aureus, and Listeria monocytogenes are commonly occurring biofilm-formers, share a similar nutritional niche, and have been isolated from common surfaces in multispecies environments. Biofilm properties, including biomass (O.D590 nm), cell concentration (log CFU/cm2), exopolysaccharide content (μg/cm2), structure, and sanitizer tolerance (sodium hypochlorite), were observed under varying nutrient (full-strength TSB and 10 % TSB) conditions on polystyrene surfaces for single and multispecies biofilm. The synergistic interactions between the bacteria in multispecies biofilm were found to be nutrient-dependent, with significantly higher (p < 0.05) biofilm formation, exopolysaccharide content, and sanitizer tolerance in high nutrient conditions (TSB) compared with low nutrient conditions (10 % TSB). The cell concentrations in the biofilm (single and multispecies) were found to be comparable between TSB and 10 % TSB. All three bacteria involved showed increased tolerance against sanitizers in the multispecies arrangement compared to their single-species counterparts, with significantly higher survival for L. monocytogenes (5.3 log CFU/cm2) in a multispecies biofilm compared to its single-species counterpart (2.3 log CFU/cm2). A positive correlation was observed between exopolysaccharide concentration and sanitizer tolerance. This study highlights the importance of taking multiple bacteria and their growth environment into account when understanding sanitizer response, as it varies in multispecies biofilm setups and according to nutrient availability.
Evaluation of single and multispecies biofilm formed in the static and continuous systems.
(Elsevier B.V., 2024-12-19) Pant K; Palmer J; Flint S
Biofilms consisting of multiple species of bacteria compared to biofilms of single species are common in natural environments including food contact surfaces. The objective of this study was to understand the biofilm formation and the efficiency of sodium hypochlorite (50 ppm/5 mins) on the single and multiple species biofilm of Pseudomonas fluorescens, Staphylococcus aureus, and Listeria monocytogenes formed on stainless steel surfaces in static and continuous systems. The cell concentration of Listeria in the dual and triple species biofilm in the continuous system (7.3-8.4 log CFU/cm2) was higher compared to the static system (4.7-4.9 log CFU/cm2) while the concentration remained consistent in the single species biofilm (6.4-6.7 log CFU/cm2) for both systems. Biofilm formed in the static system was significantly (p < 0.001) more susceptible to sodium hypochlorite than biofilm formed in the continuous system. This observation agrees with the exopolysaccharide concentration which was found to be higher in the continuous system (8.0-15.6 μg/cm2) than in the static system (3.2-6.3 μg/cm2) indicating a positive correlation between EPS production and sanitizer resistance. Epifluorescence microscopy images showed the formation of interstitial voids within the three-species biofilm and filaments in the single and dual species Listeria biofilms in the continuous system which were absent in the static system. Overall, results showed that the biofilm formation and sanitizer resistance vary due to multispecies interaction and the presence of flow and should be considered an important variable in multispecies sanitizer resistance studies.
Multispecies biofilm cities and the importance of the order of colonization
(Elsevier Ltd, 2025-09) Pant K; Palmer J; Flint S
Biofilms are sessile communities of cells embedded in the extracellular matrix of polysaccharides formed to protect themselves from adverse conditions and are attached to the biotic/abiotic surfaces. In the natural environment, the probability of bacteria existing in multispecies is higher than the bacteria existing in isolation. The first step to a stable multispecies biofilm formation is the attachment and colonization of the surface by one or more bacteria. This review aimed to understand the impact of sequential attachment in overall multispecies biofilm formation, its role in defining biofilm properties, and the possible challenges it could present during the removal and disinfection process. In several cases, the highest biofilm former attached to the surface first resulting in a stronger biofilm which explains the enhanced resistance to removal in multispecies biofilm. Following the formation of a stable biofilm, environmental variables (e.g. temperature, surface, nutrient availability), and metabolic exchange between the bacteria drive the properties of biofilm, finally resulting in sequential detachment, driven by the predominant bacteria. These insights are vital in understanding biofilm formation and spatial layering of pathogenic bacteria for efficient biocontrol and removal.
Shear stress adaptation of Listeria monocytogenes in mono and dual-species biofilms
(Elsevier Ltd, 2025-12-01) Pant K; Palmer J; Flint S
While the impact of stress on L. monocytogenes associated with food processing has been recognized in planktonic conditions, the available research overlooks the response of this pathogen in the multi-species biofilm, commonly found in food processing and manufacture. The objective of this study was to understand the effect of shear stress on L. monocytogenes in single and dual-species (with P. fluorescens) biofilm formed in a continuous turbulent flow system. In the single-species biofilm, L. monocytogenes was able to form a biofilm under the turbulent flow with cell concentration reaching 5.1 log CFU/cm2 after 48 h, where filamentous cells (27.7 μm in length) were observed. In contrast, there were no visible filaments in the dual-species biofilm, and L. monocytogenes cell concentration was significantly higher (p < 0.001) at 8.7 log CFU/cm2. The cells harvested from single-species L. monocytogenes biofilm formed under turbulent flow showed significantly (p < 0.001) lower motility and higher adhesion compared with cells harvested from planktonic and static conditions. Gene expression analysis showed significant (p < 0.001) downregulation of motB (motility), sigB (stress), and cell division (ftsX and ftsW), and upregulation of mpl (adhesion) and rodA (rod shape), indicating L. monocytogenes adaptation to shear stress. This study provides fundamental information on the multi-species biofilm formation by L. monocytogenes under stress.