Abstract
Carnobacterium maltaromaticum is frequently associated with foods having extended shelf-life due to its inhibitory activity to other bacteria. The quantification of such inhibition interactions affected by various environmental factors is limited. This study investigated the effect of environmental factors relevant to vacuum-packaged beef on inhibition between two model isolates of C. maltaromaticum, D0h and D8c, specifically D8c sensitivity to D0h inhibition and D0h inhibitor production. The effects of temperature (−1, 7, 15, 25 °C), atmosphere (aerobic and anaerobic), pH (5.5, 6, 6.5), lactic acid (0, 25, 50 mM) and glucose (0, 0.56, 5.55 mM) on D8c sensitivity (diameter of an inhibition zone) were measured. The effects of pH, glucose, lactic acid and atmosphere on D0h inhibitor production were measured at 25 °C. Sensitivity of D8c was the highest at 15 °C, under aerobic atmosphere, at higher concentrations of undissociated lactic acid and glucose, and at pH 5.5 (p < 0.001). pH significantly affected D0h inhibitor production (p < 0.001), which was the highest at pH 6.5. The effect of lactic acid depended upon pH level; at relatively low pH (5.5), lactic acid decreased the production rate (arbitrary inhibition unit (AU)/mL/h). This study provides a quantitative description of intra-species interactions, studied in in vitro environments that are relevant to vacuum-packaged beef.
Highlights
Bacteria interact in any given niche, and these interactions may have a positive or negative impact on the involved species [1]
Examining a broad spectrum of bacterial species isolated from VP beef produced at different abattoirs, we showed that cell-free supernatant (CFS) of C. maltaromaticum inhibited a wide spectrum of species, including Serratia spp., Pseudomonas spp., Leuconostoc spp. and other Carnobacterium spp
By using an agar model system, we have quantified the effects of the VP beef-related environmental factors, pH, lactic acid, glucose, temperature and atmosphere on the inhibitions between two C. maltaromaticum isolates, i.e., D8c sensitivity and D0h inhibitor production
Summary
Bacteria interact in any given niche, and these interactions may have a positive or negative impact on the involved species [1]. A type VI secretion delivery system (T6SS) is found to be utilized by Pseudomonas aeruginosa to deliver bacteriolytic effectors to other Gram-negative bacterial cells [5]. This tubular system has been identified in >80 Gram-negative bacterial genomes, including many members of the family Enterobacteriaceae [6]. Bifidobacterium bifidum, a probiotic organism that is often found in human intestines, and Listeria monocytogenes, an opportunistic pathogen, mutually promote each other’s growth [10]. According to D'Onofrio et al [11], previously uncultured bacteria from marine sediment grew on agar in the presence of readily-cultured bacteria due to the latter forming growth-promoting siderophores
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