In this study, the survival of genetically engineered microorganisms (GEMs) and their interactions with the environmental microbiota of a tropical river was investigated. Diffusion chambers were used for the in situ survival experiments with a nonplasmid containing Escherichia coli DH1 strain and two model GEMs, E. coli JM103 containing a 2.6 kilobase plasmid (pUC9) and E. coli DH1 with a 4.8 kb plasmid (pWTAla5'). Pure culture survival studies indicated that after a week in the environment a 1.0 log10 decrease in bacterial numbers occurred for both E. coli DH1, while a 3.0 log10 reduction was observed for E. coli JM103. However, a reduction of 4.0 log10 was observed for the E. coli DH1 (pWTAla5') when placed in a chamber conjointly with the resident microbiota. The data suggest that the presence of a plasmid makes no difference on the survival time of GEMs, whereas the presence of competing bacteria is ultimately what limits the survival time of GEMs in the environment.

A study was conducted to determine characteristics of unicellular microorganisms that are associated with their being indigenous to soil. The approach involved a comparison of the behavior of 12 isolates from soil and 16 from lake water. After addition to soil at approximately 0.15 MPa moisture, the population of microorganisms originally isolated from soil declined somewhat but remained larger than 10(4) g-1 for 30 days. The populations of most but not all the aquatic bacteria declined to a greater extent under identical conditions, and some were no longer detected. In soil undergoing drying, the abundance of both soil and aquatic microorganisms declined in similar fashions, and a few species could not be detected at 30 days. The resistance of soil and aquatic microorganisms as a group to starvation stress in soil and liquid did not differ. The results indicate that soil microorganisms as a group are more able to endure biological stresses in soil than are non-soil microorganisms. Because some non-soil organisms persist in non-sterile soil, the habitat of a species is an insufficient basis for assessing its ability to survive in soil.

Explores the fundamental elements affecting the presence, activity, and control of microorganisms in food. Includes the latest information on the basic biology of foodborne organisms as well as on all microbial cells, including their genes and molecules. Covers the history of microorganisms in food; the taxonomy, role and significance of microorganisms in foods; intrinsic and extrinsic parameters of foods that affect microbial growth; microorganisms in fresh and processed meats and poultry, seafoods, fermented dairy products; fresh and fermented fruit and vegetable products, and miscellaneous food products; determining microorganisms and/or their products in foods; food preservation and some properties of psychrotrophs, thermophiles, and radiation-resistant bacteria; microbial indicators of food safety and quality, principles of quality control, and microbiological criteria; foodborne diseases; etc. Of interest to food scientists as well as to students taking a food microbiology course.

Mixed ruminal microorganisms were harvested from a lactating dairy cow and preserved frozen or lyophilized. Fermentation characteristics of freshly strained ruminal fluid, frozen microorganisms, or lyophilized microorganisms were evaluated during a 24-h pre-incubation and a 4-h incubation with test proteins. Differences observed during the first 4 to 6 h in total amino acid concentration, optical density, pH and VFA concentrations, acetate:propionate ratio, and lactate concentration largely disappeared later in the pre-incubation. Protein degradation rates determined for expeller and solvent meals were .015 and .092 h-1, .015 and .101 h-1, and .005 and .019 h-1, with fresh ruminal fluid, frozen microorganisms, and lyophilized microorganisms, respectively. Regression of degradation rates obtained with fresh ruminal fluid on those obtained with pre-incubated, frozen microorganism indicated the two methods were well correlated (r2 .98 and .94 in two experiments). Mean in vitro degradability obtained for 17 feeds using pre-incubated, frozen microbes was 89% of that obtained using the in situ method; however, in situ degradation rates for these same feeds averaged only 67% of those obtained using frozen microorganisms. Ruminal undegraded protein values for nine samples of heated soybeans and soybean meal, determined using frozen microbes, were overestimated relative to in vivo values (in vivo = 1.1 + .8 in vitro; r2 = 77). These results indicated that ruminal microorganisms can preserved by freezing and used as the inoculum for vitro determination of ruminal protein degradation after overnight pre-incubation.

Many microorganisms in nature have evolved new genes which encode catabolic enzymes specific for chlorinated aromatic substrates, allowing them to utilize these compounds as sole sources of carbon and energy. An understanding of the evolutionary mechanisms involved in the acquisition of such genes may facilitate the development of microorganisms with enhanced capabilities of degrading highly chlorinated recalcitrant compounds. A number of studies have been based on microorganisms isolated from the environment which utilize simple chlorinated substrates. In our laboratory, a selective technique was used to isolate microorganisms capable of degrading highly chlorinated compounds, such as 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), as sole sources of carbon and energy. This article summarizes the genetic and biochemical information obtained regarding the pathway of degradation, the mechanism of recruitment of new genes, and the organization of the degradative genes. In addition, we discuss the potential practical application of such microorganisms in the environment.

Ruminal microorganisms, preserved either lyophilized or frozen, were compared with freshly strained ruminal fluid for proteolytic activity and as inoculum source for determination of ruminal protein degradation rates by the inhibitor in vitro method. Dialysis and glycerol addition had no effect on the proteolytic activity of preserved microorganisms. Net release of NH3 and total amino acids from protein using the fluid plus particle-associated microorganisms was higher than that found using the fluid-associated microorganisms alone. Method of inoculum preservation altered total proteolytic activity, but harvesting bacteria using centrifugal force greater than 5,000 X g did not increase proteolytic activity of the pellet. The proposed method for harvesting and preserving microorganisms consisted of centrifuging strained ruminal fluid at 5,000 X g (30 min at 4 degrees C), stirring the pellet in a 50:50 (vol/vol) solution of glycerol-McDougall's buffer for 15 min, and then storing at -20 degrees C. Protein degradation rates in incubations with preserved microorganisms were four to eight times slower than when using fresh ruminal fluid; however, feed proteins were ranked similarly for degradation rate. Preincubating the preserved microorganisms reduced blank concentrations of NH3 and total amino acid and increased protein degradative activity of the preserved inoculum. Degradation rates with preincubated, preserved inocula were similar to those obtained using fresh ruminal fluid. These results indicated that mixed ruminal microorganisms can be preserved by freezing and, after a preincubation period of 6 h, used as the inoculum source for in vitro estimation of ruminal protein degradation.

The maximum number of proteolytic microorganisms and the highest proteinase activity were detected in the humus horizon. These indicators of soil biological productivity declined with depth. Proteolytic microorganisms were most numerous in mid-vegetation and least numerous in the second half of vegetation in both horizons, numerical values being lower in the horizon of 20-40 cm. Proteinase activity proved the highest in mid-vegetation and the lowest in the second half of vegetation in the horizon of 0-20 cm. In the horizon of 20-40 cm, a constant decrease in proteinase activity was noticed all vegetation long.

Limited land and insufficient technicians to operate a wastewater treatment system are main restrictions for many factories. Therefore, an ideal wastewater treatment method for a small or land-limited factory must possess merits such as high performance efficiency, high organic loading rate, little odor, simple operation, easy maintenance, and little land required (simultaneously). An entrapment technique to immobilize mixed microorganisms to treat organic wastewater, which was developed in the present work, possesses these characteristics. This project was done on a laboratory scale. The microorganisms were activated sludge (an undefined mixture of microorganisms obtained directly from a domestic wastewater treatment plan) and the mixed microorganisms were immobilized in cellulose triacetate by means of an entrapment technique to treat organic wastewater from food industry. After wastewater was treated by this system, the SCOD (soluble COD) removal efficiency of 81% evaluated samples exceeded 80% in 1.5+/- 0.9 g SCOD/L/d of the volumetric loading rate and 7-10 h for the hydraulic retention time. This wastewater treatment method can be applied to other organic industrial wastewater.