The adhesion of seven meat spoilage bacteria to model meat surfaces (thin fat and tendon slices) was studied in a specially designed flow chamber. In general, adhesion was not influenced by the physiological age of the cells and was not correlated with the cell surface characteristics (electrical charge, hydrophobicity) of the organisms. Also, adhesion data did not corroborate the predictions based on changes in the free energy of adhesion, calculated from contact angles and surface tension measurements. A more detailed study of the adhesion of Pseudomonas fluorescens to tendon was subsequently undertaken. Neither physiological activity nor the presence of flagella was found to be essential for adhesion. Selective chemical alterations of the cell surface pointed to no direct implication of carboxyl or amino groups in an adhesive bond with tendon. These groups may participate in adhesion, however, through electrostatic interactions as suggested from the variations of adhesion with ionic strength.

Beef tendons were sectioned into 60 mum-thick slices (1cm 2) and deposited onto glass cover slips. These meat slices were flooded with a cell suspension of either Pseudomonas fluorescens, Enterobacter agglomerans, or Moraxella osloensis in distilled water and adhesion allowed to occur. The adhesion experiments were also conducted on agar-covered slides to evaluate the effect of the nature of the substratum on adhesion. The non-adherent organisms found on either surface tested (meat or agar) were removed by flushing liquid over the slide. The slides were then incubated in a moist atmosphere at 30°C. Once the presence of microcolonies had been established microscopically, the slides were mounted into flow chambers and the surface flushed with distilled water to ascertain the effects of bacterial proliferation on adhesion. In other experiments, the influence of acetic, citric, and lactic acid rinses on cell adhesion and subsequent cell proliferation was evaluated. Microcolony formation was shown to reduce the adhesion strength of Enterobacter agglomerans and, to a lesser extent, that of Moraxella osloensis while increasing that of Pseudomonas fluorescens. The probable determinant of adhesion strengths of microcolonies is exopolymer synthesis. A minimal decrease in bacterial adhesion and microcolony formation was observed with the use of organic acid rinses. The bactericidal activity and effect on bacterial proliferation increased with increasing concentration and rinse times of the organic acids. The extent of the adhesion reductions suggests that the preservation action of organic acids is due to cell death and not adhesion inhibition.

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Lactoferrin (Lf) is an iron binding protein produced in mammals. It has antimicrobial and immunomodulatory properties. Some bacteria that regularly colonize mammalian hosts have adapted to living in high Lf environments. Helicobacter pylori, which inhabits the human gut, was chosen as a model organism to investigate how bacteria may adapt to Lf. H. pylori was able to use iron from fully saturated human Lf (hLf) in various low iron media, achieving growth levels similar to the ironreplete control. Partially saturated hLf decreased growth, yet both partially saturated bovine Lf (bLf) and hLf were able to increase internalization of bacteria into mammalian tissue culture cells. A substantially larger increase in internalization was seen when bacteria were supplemented with hLf in low iron conditions, possibly mediated by iron-regulated cellular receptors or bacterial lactoferrin binding proteins. In eukaryotes, Lf is known to bind and facilitate internalization of DNA into cells and sometimes the nucleus, and upregulate gene expression. Here, one hundred bacterial genomes were surveyed for known Lf binding sites as an indication that Lf had similar functions using bacterial DNA. While the frequency and location of Lf binding sites suggest they occur at random, their presence in all genomes suggests that Lf may be able to act as a vector for bacterial DNA, and facilitate the movement of genes between species. Lf is being widely considered for commercial and therapeutic uses, with significant interest in producing it in genetically modified organisms (GMO). Widespread production and use of Lf could increase the number of bacteria that are adapted to it. How Lf interacts with bacteria adapted to it, and the ability of it to act as a DNA vector, may have relevance for GMO risk assessment.