Utilization of substrates by bacterial communities (biofilm) as they develop on stored chicken meat samples

USDA, Richard B. Russell Agricultural Research Center, Athens, Georgia 30604, USA.

Understanding and controlling the metabolic processes of microorganisms associated with chicken meat can lead to safer poultry products with a longer shelf life. The objective of the present study was threefold: 1) to determine the feasibility of using 96-well Biolog GN microtiter plates to assess substrate utilization profiles of bacterial communities (biofilm) as they develop on poultry products, 2) to identify substrates metabolized by microbial populations associated with stored chicken meat, and 3) to compare the substrate utilization profiles of biofilm communities as they develop on meat stored at 4 C (refrigeration temperature) for up to 5 d or at 13 C (a temperature common in poultry processing areas) for 2 d. The protocol used herein for preparing inocula for microplates was acceptable for the collection of optical density values (590 nm) in microplate wells as an indicator of microbial substrate utilization over time. Data from treatment of chicken meat samples using this protocol indicate that most of the 95 substrates tested were metabolized by microbial communities present as early as 1 d after storage at 4 or at 13 C. However, the rapidity (incubation time required for initial substrate utilization) and frequency (percentage of plates positive for transformation of an individual substrate) of metabolism of the substrates by the biofilm communities varied from 4 to 164 h of plate incubation and from 17 to 100% of microplates, respectively. At 13 C, polymers were the most rapidly metabolized substrate group, followed by carbohydrates, carboxylic acids, miscellaneous or amino acids, and amides or amines. Initial utilization of these substrate groups at 4 C occurred within a consistently shorter period (24 h of plate incubation). The frequency of metabolism of each individual substrate group varied only 3 to 16% between samples stored at 4 and 13 C. However, a greater difference in frequency of utilization of some individual substrates was noted. Such divergences may be useful in characterizing biofilm communities implicated in pathogenicity or affecting food quality of poultry products.