The Antibiotic Epidemic Antibiotic Resistance
Seven of the twelve genera of lactic acid bacteria, Lactobacillus, Lactococcus, Leucon-ostoc, Oenococcus, Pediococcus, Streptococcus, and Tetragenococcus, are used directly in food fermentations. Although Enterococcus sp. are often found in fermented foods (e.g., cheese, sausage, fermented vegetables), except for a few occasions, they are not added directly. In fact, their presence is often undesirable, in part, because they are sometimes used as indicators of fecal contamination and also because some strains may harbor mobile antibiotic-resistance genes.
The possible relationship between antibiotic resistance and productivity may be used to advantage in the selection of high-producing mutants by culturing the survivors of a mutation treatment in the presence of a high level of the end product. Those strains capable of growth in the presence of a high level of the antibiotic may also be capable of high productivity in the idiophase. This approach has been used successfully for antifungal agesterols (Bu'Lock, 1980), streptomycin (Woodruff, 1966) and ristomycin (Trenina and Trut-neva, 1966) but without success for novobiocin (Hoeksema and Smith, 1961).
For the efficient production of recombinant proteins in E. coli, the primary consideration is the choice of suitable expression vector. In general, the expression vector should contain several necessary elements such as origin of replication, antibiotic resistance gene or other selectable marker, promoter and transcription terminators etc.
Most industrial strains of Acetobacter contain plasmids,whose loss could conceivably account for phenotypic changes. However, except for the presence of antibiotic resistance genes, functions for other plasmid-borne genes have not been identified, and most plasmids are considered to be cryptic and not essential for acetic acid formation.
Acylated homoserine lactones serve as one class of signal molecule in bacterial communication. These molecules and their derivatives have been linked to control of bioluminescence, Ti plasmid transfer, production of virulence factors, antibiotic resistance, and swarming motility (94). Higher life forms have evolved mechanisms to interfere with such signaling processes. For example, certain seaweeds and sea grasses produce halogenated furanones, structurally similar to acylated homoserine lactones, that interfere with the swarming process and have been shown effective as antifoulants and antimicrobials (95). Givskov et al. (96) illustrated that two different furanones derived from the seaweed Delisea pulchra could progressively inhibit and eliminate the swarming behavior of Serratia li-quefaciens as concentrations were increased from 0 ig mL to 100 ig mL (concentrations far too low to affect the growth of the bacteria).
Single-crossover recombination showing integration of an intact integration vector into the host chromosome at the site of the target gene. Part or all of the target gene is duplicated as a result of the integration event. The inclusion of a controllable promoter upstream of the target gene fragment on the vector allows for controllable gene expression of the 3' copy of the gene or any genes downstream in the same operon. AlP, selectable antibiotic resistance gene. Single or Campbell-type integration events generally use E. coli-based plasmid vectors that are not able to replicate in gram-positive bacteria but that include an antibiotic resistance gene that can be selected in B. subtilis. A fragment of B. subtilis DNA ( 0.4 kb) is cloned via E. coli into the integrational vector, which is then transformed into B. subtilis. Selection for an antibiotic-resistant gene results in transformants in which the vector has integrated into the host chromosome via a single-crossover...