Fate and activity of microorganisms introduced into soil.

Introduced microorganisms are potentially powerful agents for manipulation of processes and/or components in soil. Fields of application include enhancement of crop growth, protection of crops against plant-pathogenic organisms, stimulation of biodegradation of xenobiotic compounds (bioaugmentation), and improvement of soil structure. Inoculation of soils has already been applied for decades, but it has often yielded inconsistent or disappointing results. This is caused mainly by a commonly observed rapid decline in inoculant population activity following introduction into soil, i.e., a decline of the numbers of inoculant cells and/or a decline of the (average) activity per cell. In this review, we discuss the available information on the effects of key factors that determine the fate and activity of microorganisms introduced into soil, with emphasis on bacteria. The factors addressed include the physiological status of the inoculant cells, the biotic and abiotic interactions in soil, soil properties, and substrate availability. Finally, we address the possibilities available to effectively manipulate the fate and activity of introduced microorganisms in relation to the main areas of their application.     

Fate of exogenous recombinant plasmids introduced into mouse and human cells.

We have constructed a number of plasmids selectable in both E. coli and mouse or human cells. Human DNA sequences were inserted and the recombinant plasmids were used to transfect either mouse or human cells by the Ca-phosphate precipitation technique. We have observed that: (i) competent cells uptake large amounts of plasmid DNA; (ii) input plasmids persist in transformed mammalian cells as free unreplicating circular molecules for up to 20 generations; such persistence does not depend on the presence of selective markers; (iii) plasmids incorporated into mouse L-cells undergo widespread rearrangements (in the absence of replication) entailing mostly deletions of both human and bacterial sequences which yield smaller products; the latter appear to be more stable in a subsequent transformation cycle. Surprisingly such rearrangements are almost totally absent in transformed human KB-cells. This property of human KB-cells may prove useful for the development of a vector apt at cloning and expressing human DNA sequences. Unlike what has been observed in yeast, no "autonomously replicating sequence" can be detected in mammalian cells by randomly cloning human DNA sequences into a selectable plasmid and screening for an increased transformation efficiency.     

Fate determination of fetal Leydig cells

Leydig cell (LC) is one of the most important somatic cell types in testis, which localized in the interstitium between seminiferous tubules. The major function of Leydig cells is to produce steroid hormone, androgens. LC differentiation exhibits a biphasic pattern in rodent testes, which are divided into two different temporal mature populations, fetal Leydig cells (FLCs) and adult Leydig cells (ALCs). FLCs are transiently present in fetal testes and undergo involution or degeneration after birth. FLCs are completely devoid and replaced by ALCs in adult testes. Comparing to ALCs, FLCs display unique morphology, ultrastructure and functions. The origin of FLCs has been debated for many years, but it is still a mystery. Many factors have been reported regulating the specification, proliferation and differentiation of FLCs. FLCs degenerate in a few weeks postnatally, however, the underlying mechanism is still unknown. In this review, we will focus on the fate determination of FLCs, and summarize the resent progress on the morphology, ultrastructure, function, origin and involution of FLCs.     

Regulated expression of cloned human fetal A gamma-globin genes introduced into murine erythroleukemia cells

We have analysed the expression of cloned human fetal gamma-globin genes introduced into murine erythroleukemia cells by a protoplast fusion procedure. Both the wild-type a gamma-globin gene and a mutant derivative related to a phenotype of hereditary persistence of fetal hemoglobin were studied. In both cases the level of gamma-globin mRNA increased by a factor of approximately sevenfold when erythroid cell differentiation was induced by treatment with hexamethylenebisacetamide. Thus, the regulation of the expression of the cloned fetal A gamma-globin gene in murine erythroleukemia cells resembled that of cloned adult beta-globin genes.     

Transformation in Bacillus subtilis. Fate of newly introduced transforming DNA

Summary Donor deoxyribonucleic acid (molecular weight 5-8×10⁷) introduced into competent cells of Bacillus subtilis is converted to molecules with a weight average molecular weight of 9×10⁶. These molecules, having little transforming activity, constitute in all probability eclipse phase DNA. At least part of the DNA is transiently complexed with a cellular component, changing its buoyant behaviour in CsCl gradients. When shortly after uptake of donor DNA the total DNA extracted from recipient cells is sheared to a molecular weight of 8×10⁶ or less, no eclipse phase is discernable. Donor marker frequencies in sheared, reisolated DNA mixtures decrease by a factor of 4 as a function of time of incubation of the transforming cells. This indicates that only 25% of the irreversibly absorbed DNA is finally integrated into the recipient genome.     

Ranking introduced into phenological recording

Generally, phenological recording is based on the recognition of separate phases of development in the organism of interest. In the present study samples were ranked with respect to the stage of bud or leaf development reached at the time of sampling. In April 1982 budding and leaf development of all species of trees and shrubs were recorded over 2 km² of the northeastern slope of Nävlingeåsen, a horst in southernmost Sweden. During 3 days, of which the first two were consecutive, the author walked a stretch of 12 km, divided into 107 sections. In each of these the first living twig at about 1.5 m above ground was sampled for each species. At the end of the day all twigs from the same species were ranked by two persons independently. The ranks were normalized, and a mean calculated for each section. To reduce the impact of natural variation within a species, and also the influence of microclimate where species cluster, the ranks of the sections were smoothed by weighted moving averages. Using three localities which were investigated twice as fixed points, the ranking lists of separate days were integrated into a single system. A time lag of 4 or 5 days in the onset of spring was established between different localities.     

Survival ofFrankia strains introduced into soil

Factors affecting the establishment of Alnus/Frankia symbioses were studied partly by following the survival ofFrankia strains exposed to different soil conditions, and partly by investigating the effect of pH on nodulation. TwoFrankia strains were used, both of the Sp⁻ type (sporangia not formed in nodules). One of the strains sporulated heavily, while the other formed mainly hyphae. The strains originated fromAlnus incana root nodules growing in soils of pH 3.5 and 5.0. The optimum pH for their growth in pure culture was found to be 6.7 and 6.2, respectively. The strains were introduced into twoFrankia-free soils, peat and fine sand. Their survival, measured as the persistance of nodulation capacity using the plant infection technique, was followed for 14 months. The survival curves of the strains were similar despite the morphological differences between the strains in pure culture. The nodulation capacities declined over time both at 14 and 22°C. Survival was better in soils limed to a pH above 6 than in soils at their original pH (peat 2.9, fine sand 4.2). The effect of pH on nodule formation in Alnus seedlings by theFrankia strains was studied in liquid culture. The number of nodules increased linearly within the pH range studied (3.5–5.8). No nodules were formed at pH 3.5.     

Bovine fetal fluid cells in vitro: Fate and fetal sex prediction accuracy

Summary The in vitro fate of bovine fetal fluid cells and the efficiency of fetal sex prediction from cultures of these cells are studied using aspirates from live animals and pregnant uteri collected from the slaughterhouse. Over 70% of bovine amniotic fluid samples aspirated from pregnant uteri at the time of slaughter yielded cultures adequate for chromosome analysis, whereas only 10% of allantoic fluid samples produced growth of cells satisfactory for chromosome analysis. Fetal sexing accuracy was 100% in all samples studied. Seven readily recognizable cell types were noted in cultures of fetal fluid cells obtained at various stages of gestation. In a majority of cases, the in vitro morphology of cells from both fetal cavities was similar to that observed in primary human amniotic fluid cell cultures.     

The viability of bifidobacteria introduced into kimchi

The viability of bifidobacteria in mul-kimchi, a type of kimchi with added water, was investigated under various conditions. When a mul-kimchi preparation was inoculated with five strains of Bifidobacterium at a concentration of 10(7) cfu ml-1, Bif. longum JK-2 showed the highest viability, maintaining a population of 10(6) cfu ml-1 after 1 week at 4 degrees C. The influence of NaCl concentration and initial pH on viability was further investigated in mul-kimchi inoculated with Bif. longum JK-2; NaCl concentrations greater than 3% (w/w) reduced viability considerably. In kimchi started with an initial pH of 6.5, the cells showed the highest survival. When mul-kimchi containing 2% NaCl (w/w) was inoculated with 10(8) cfu ml-1 Bif. longum JK-2, there was a 10-fold reduction in viability during 10 d of incubation at 4 degrees C. These results demonstrate acceptable levels of the organism in the product, suggesting the possible use of selected strains of bifidobacteria in commercial kimchi production.     

Physical basis for the application of ferromagnetics introduced into body

The review deals with some medico-biological problems of ferromagnetics applications with the use of physical fields effect (permanent and alternating magnetic fields, high frequency and laser radiation). The main aspects are the following: magnetic fluid as roentgenocontrast, substances; magnetically controlled drug delivery systems; magnetic microspheres with immobilized antibodies; thermo-magnetic cancer surgery; magnetic particles as a tool for subcellular structure investigation; magnetic particles distribution and removal from the organism.     

Explanation for the decline of bacteria introduced into lake water

The sizes of the populations of individual bacterial species diminished following their addition to water from lakes with different trophic levels at temperatures of 5, 10, 15, and 30°C. Some species persisted after their initial reduction in cell numbers, but others were undetectable after 3 to 15 days. The decline of these introduced bacteria was not a result of their inoculation at higher densities than are found in nature. The death of most of the test species was not the result of starvation, abiotic factors, bdellovibrios, or bacteriophages. Despite the presence of lytic bacteria, the lake water did not have lytic activity against the test species. Protozoan predation was a significant factor in the fall in bacterial population sizes because protozoa increased in numbers as the bacterial density fell, the suppression of protozoa led to the elimination or delay of the decline of the bacteria, and the addition of protozoa to lake water in which indigenous protozoa were suppressed produced the same pattern of bacterial elimination as in untreated lake water.