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Biomedical subjects

L E Casida

Publications and source records attributed to L E Casida.

At least 19 recordsLinked to original sources
PubMed1992

Competitive ability and survival in soil of pseudomonas strain 679-2, a dominant, nonobligate bacterial predator of bacteria.

A copper-resistant, nonobligate, bacterial predator of bacteria was isolated from soil. It was a Pseudomonas species, designated strain 679-2. It attacked most other nonobligate bacterial predators and hence could control their predatory and other activities in nature. It also inhibited various fungi. It attached to prey cells and produced a toxic, copper-related, growth initiation factor like that produced by Cupriavidus necator. In addition, it produced a second, novel compound that was both antibacterial and antifungal. Strain 679-2 appeared to have only a very limited natural occurrence. It was found only in the soil from one small area in one field. It was absent on the leaves of the plant species that were examined. Regardless of its rarity, however, it was highly competitive in soil. An inoculum consisting of only a few cells added to soil multiplied rapidly to become a major component of the soil microflora within 24 h. A small amount of glutamic acid could be added along with the cells to stimulate production of the toxic compounds noted above, but this was not necessary. After this multiplication, or when large numbers of cells were added to soil, the numbers decreased only slowly during the next several months. Cell survival also was good on plant leaves. The survival in soil and on plant leaves occurred in both laboratory and field experiments. Other than desiccation, the natural mechanism for controlling the numbers or activities of strain 679-2 in soil is not known. The various characteristics of this bacterium, as noted above, are of particular interest because they indicate a possible use of the cells or inhibitor compounds for controlling organisms in soil or on plant surfaces.

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PubMed1989

Protozoan Response to the Addition of Bacterial Predators and Other Bacteria to Soil.

Representatives of several categories of bacteria were added to soil to determine which of them might elicit responses from the soil protozoa. The various categories were nonobligate bacterial predators of bacteria, prey bacteria for these predators, indigenous bacteria that are normally present in high numbers in soil, and non-native bacteria that often find their way in large numbers into soil. The soil was incubated and the responses of the indigenous protozoa were determined by most-probable-number estimations of total numbers of protozoa. Although each soil was incubated with only one species of added bacteria, the protozoan response for the soil was evaluated by using most-probable-number estimations of several species of bacteria. The protozoa did not respond to incubation of the soil with either Cupriavidus necator, a potent bacterial predator, or one of its prey species, Micrococcus luteus. C. necator also had no effect on the protozoa. Therefore, in this case, bacterial and protozoan predators did not interact, except for possible competition for bacterial prey cells. The soil protozoa did not respond to the addition of Arthrobacter globiformis or Bacillus thuringiensis. Therefore, the autochthonous state of Arthrobacter species in soil and the survival of B. thuringiensis were possibly enhanced by the resistance of these species to protozoa. The addition of Bacillus mycoides and Escherichia coli cells caused specific responses by soil protozoa. The protozoa that responded to E. coli did not respond to B. mycoides or any other bacteria, and vice versa. Therefore, addition to soil of a nonsoil bacterium, such as E. coli, did not cause a general increase in numbers of protozoa or in protozoan control of the activities of other bacteria in the soil.

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PubMed1988

Response in Soil of Cupriavidus necator and Other Copper-Resistant Bacterial Predators of Bacteria to Addition of Water, Soluble Nutrients, Various Bacterial Species, or Bacillus thuringiensis Spores and Crystals.

Soil was incubated with various species of bacteria, Bacillus subtilis, or Bacillus thuringiensis spores and crystals. These were added to serve as potential prey for indigenous, copper-resistant, nonobligate bacterial predators of bacteria in the soil. Alternatively, the soil was incubated with soluble nutrients or water only to cause potential indigenous prey cells to multiply so the predator cells would multiply. All of these incubation procedures caused excessive multiplication of some gram-negative bacteria in soil. Even greater multiplication, however, often occurred for certain copper-resistant bacterial predators of bacteria that made up a part of the gram-negative response. Incubation of the soil with copper per se did not give these responses. In most cases, the copper-resistant bacteria that responded were Cupriavidus necator, bacterial predator L-2, or previously unknown bacteria that resembled them. As was the case for C. necator and L-2, these new bacteria did not use glucose, had white colonies, produced copper-related growth initiation factor (GIF), and attacked B. thuringiensis spores on laboratory media. The results were different, however, when B. thuringiensis spores and crystals per se were added to the soil. The copper-resistant bacterial response in the soil did not, to any extent, include C. necator-like bacteria. Instead, the main copper-resistant bacterial predators that developed had yellow colonies and did not resemble C. necator or L-2 in other ways. They were not seen before, and they did not develop on the addition of B. subtilis spores to soil. Apparently, they could not produce a C. necator-like GIF. Nevertheless, they did respond very quickly to B. thuringiensis spores and crystals in soil, as if a GIF of some sort were involved. These results suggest that, under various conditions of soil incubation, gram-negative bacterial predators of bacteria multiply and that several copper-resistant types among them can be detected, counted, and isolated by plating dilutions of the soil onto media containing excess copper.

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PubMed1987

Technique for Estimating Low Numbers of a Bacterial Strain(s) in Soil.

A technique is described for obtaining most probable number estimates of the number of cells of a bacterial strain(s) when it is present in low numbers in the soil. The technique is based on the bacteriophage response that is elicited when a known number of bacteriophage for the bacterium of interest is incubated with soil dilutions in a nutrient broth. The technique was evaluated for use with gram-negative bacteria.

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PubMed1987

Relation to copper of N-1, a nonobligate bacterial predator.

Nonobligate bacterial predator strain N-1 was highly resistant to copper. In fact, it required more than minimal amounts of copper to initiate growth, but not for growth that followed growth initiation. Strain N-1 made a peptide growth initiation factor (GIF) to marshal copper from its environment for growth initiation. Production of this GIF occurred before the onset of growth initiation, but production was shut down if excess copper was present. At high copper levels, the time required for onset of growth initiation was directly related to the amount of copper that was present. At low copper levels, a similar graded response occurred for increments of added GIF. Agromyces ramosus is a predator in its own right, but it also is a prey species for strain N-1. A. ramosus was found to be very sensitive to copper and to the copper GIF produced by N-1. It is possible that the copper GIF is the means used by N-1 to kill A. ramosus.

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PubMed1986

Gram-negative versus gram-positive (actinomycete) nonobligate bacterial predators of bacteria in soil.

The existence of nonobligate bacterial predators of bacteria in soil has been previously reported. Several additional predators were isolated from soil and tested for predation in situ in soil by use of the indirect bacteriophage analysis technique. The trials were conducted with nutritionally poor and nutritionally enriched soil. Certain of the predators that were gram negative were found to attack a range of both gram-positive and gram-negative host cell species, including at least some of the other predator bacteria, both gram positive and gram negative. The attack occurred in both the nutritionally poor and rich soils, but in some instances it was somewhat depressed in the rich soil. This may be due to the nonobligate nature of the predation. The gram-positive predators attacked a relatively narrow range of prey species, and the attack occurred only in the nutritionally rich soil. In addition, the gram-positive predators were subject to attack by certain of the gram-negative predators. These gram-negative predators therefore appeared to play a dominant role in the control of bacterial numbers in soil.

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PubMed1985

Study of Bacillus subtilis Endospores in Soil by Use of a Modified Endospore Stain.

The Schaeffer-Fulton endospore stain was modified so that it would stain Bacillus subtilis endospores in soil smears. The modified stain differentiated among dormant spores, spores undergoing activation, and spores which had germinated but had not yet shown outgrowth. These differentiations were seen for spores in soil and for pure spore preparations in the laboratory. This stain was used to show reversible B. subtilis spore activation promoted by an Ensifer adhaerens-like indigenous bacterium in soil and by pure cultures of E. adhaerens added to spores in the laboratory. Under the specific conditions in the laboratory, spore germination did not proceed beyond the activation stage, and relatively little change occurred in the numbers of both E. adhaerens and B. subtilis. This was also true in soil, although some germination with destruction of spores and vegetative cells did occur if the soil had been nutritionally enriched by preincubation with incorporated ground alfalfa.

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PubMed1985

Survival of Bacillus thuringiensis Spores in Soil.

Bacillus thuringiensis spores and parasporal crystals were incubated in natural soil, both in the laboratory and in nature. During the first 2 weeks, the spore count decreased by approximately 1 log. Thereafter, the number of spore CFU remained constant for at least 8 months. B. thuringiensis did not lose its ability to make the parasporal crystals during its residence in soil. Spore survival was similar for a commercial spore-crystal preparation (the insecticide) and for laboratory-grown spores. In contrast to these results, spores that were produced in situ in soil through multiplication of added vegetative cells survived for only a short time. For spore additions to soil, variations in soil pH had little effect on survival for those spores that survived the first 2 weeks of incubation. Also without effect were various pretreatments of the spores before incubation in soil or nutritional amendment or desiccation of the soil. Remoistening of a desiccated soil, however, caused a decrease in spore numbers. Spores incubated in soil in the field did not show this, but the degree of soil desiccation in nature probably never reached that for the laboratory samples. The good survival of B. thuringiensis spores after the first 2 weeks in soil seemed to be a result of their inability to germinate in soil. We found no evidence for the hypothesis that rapid germination ability for spores in soil conferred a survival advantage.

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PubMed1983

Ensifer adhaerens Predatory Activity Against Other Bacteria in Soil, as Monitored by Indirect Phage Analysis.

An indirect phage analysis procedure was used to detect and follow the activity of the bacterial predator Ensifer adhaerens in situ in natural soil. The soil was percolated with an aqueous suspension of washed bacterial host cells so that the E. adhaerens cells naturally present in the soil would multiply in response to the host cells. The natural phage development which ensued against these multiplying E. adhaerens cells in the soil was then monitored by noting plaques which developed when the percolation fluid was plated with laboratory strains of E. adhaerens on laboratory media. The activities of the other members of the predation system that includes E. adhaerens (Streptomyces sp. strain 34 and a myxobacter) could not be monitored directly by phage analysis because phage were not found for them. Indirect monitoring was possible, however, because they were susceptible to attack by E. adhaerens. In general, the results were in agreement with previous observations by other methods of the predation sequence. E. adhaerens attacked Micrococcus luteus, Streptomyces sp. strain 34, and the myxobacter but did not attack several other possible species of hosts. It also did not respond to percolation of the soil with various nutrient solutions. E. adhaerens phage activity was not present in half of the soils percolated with M. luteus cells. This seemed to reflect too great a phage-host specificity for the technique as regards these soils, because E. adhaerens-like bacteria other than the strains used for plaquing were present in at least some of these soils. Although E. adhaerens did not attack Escherichia coli or Pseudomonas aeruginosa in soil, there was an overproduction of E. adhaerens phage if these bacteria were percolated simultaneously with M. luteus cells. The possibility is discussed that this represents an activation by M. luteus (or by a heat-extractable factor from it) of other bacterial predators that attack E. coli or P. aeruginosa and that these predators subsequently are themselves attacked by E. adhaerens.

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PubMed1983

Interaction of Agromyces ramosus with Other Bacteria in Soil.

Agromyces ramosus occurs in very high numbers in most soils and, based on studies of laboratory isolates, does not require host cells for growth. Nevertheless, it attacked and destroyed most of the gram-positive and gram-negative bacterial species tested as possible host organisms. A. ramosus also attacked and destroyed Saccharomyces cerevisiae. The possibility of attack on fungi was unclear. Among the bacteria serving as hosts were the important soil species Azotobacter vinelandii, Rhizobium leguminosarum, Rhizobium meliloti, and Agrobacterium tumefaciens. Dead cells were not attacked. A. vinelandii cysts were attacked but left unharmed. To some extent, A. vinelandii seemed to survive this attack by encysting. Attack by A. ramosus occurred in natural soil and over a broad range of nutritional levels in laboratory media. The attack did not seem to be a means for obtaining an increased supply of commonly available nutrients. Instead, it seemed to be a means of obtaining something produced, perhaps in small amounts, by a variety of organisms, but not by all organisms. Several types of culture filtrates were tested for activity. The filtrates neither stimulated nor inhibited the growth of A. ramosus or the host organisms. The availability of catalase activity in host organisms did not seem to be involved. It is not known whether the attack by Agromyces ramosus in soil can be manipulated to cause a decrease in numbers of Agrobacterium tumefaciens or other pathogens without simultaneously depressing the numbers of beneficial organisms in this habitat.

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PubMed1982

Death of Pseudomonas aeruginosa in soil.

When incubated in natural (nonsterilized) soil, Pseudomonas aeruginosa died initially at a rate which approximated the rate for starvation of a pure culture in buffer. Predation by other soil microbes or phage did not appear to be involved, and pyocyanin either was not produced or was ineffective. The initial rate of death was followed by a second, considerably slower rate. Cells initially added in low numbers to soil also underwent biphasic death as above. Slow drying of the soil caused a period of rapid soil death of P. aeruginosa, but this then slowed to give residual numbers and a death rate similar to the second death rate noted for soil not allowed to dry. The cells in the dry soil had not changed genetically to a desiccation-resistant form. Pseudomonas aeruginosa died out completely in a relatively short time when the soil was first quickly dried to a water content similar to that obtained initially through slow drying and then further allowed to dry slowly. These observations appear to point to a dormant form, in some ways resembling a cyst, for P. aeruginosa in soil.

Humidity↗
PubMed1981

Isolation of arthrobacter bacteriophage from soil.

Soil was percolated with water and various nutrient solutions, and then the percolates were analyzed for bacteriophages which produced plaques on various Arthrobacter strains. The water percolates did not contain detectable phage. In contrast, phages for A. globiformis strains ATCC 8010 and 4336, and for several recent Arthrobacter species soil isolates, were easily detected in nutrient broth, soil extract, and cation-complete medium percolates. These percolates did not contain phage that produced plaques on A. oxydans and a recent Arthrobacter species soil isolate. Percolation with a selective nicotine-salts solution was required for demonstrating phage for these bacteria. None of the percolates contained phage for five additional named Arthrobacter species. In addition, phages were not detected for A. crystallopoietes in a 2-hydroxypyridine percolate of soil. Based on their lytic spectra, the phage isolates from this soil were relatively host specific.

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PubMed1980

Death of Micrococcus luteus in Soil.

Micrococcus luteus cells died relatively quickly when they were added to natural soil. The results were similar for soil in nature and as soil samples in the laboratory. The cells died more quickly when nutrients were added to the soil. Those cells that survived soil residence exhibited a temporary lengthening of the time required for colonial growth and pigment formation on laboratory media. They had not gained increased survival capability, however. This was evident when they were retested in soil. Good survival of the M. luteus cells was noted when the soil was incubated at lowered temperatures. Some protection to the cells was provided by slow drying of the soil during incubation or by addition of NaCl. Microscopic examination of the soil revealed that the M. luteus cells were being physically destroyed and that two different bacteria were growing in the areas where the cells had lysed. It was suggested that bacterial predators in the soil might be associated with the death of the M. luteus cells.

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PubMed1980

Bacterial Predators of Micrococcus luteus in Soil.

Micrococcus luteus cells died relatively rapidly when they were added to natural soil. Microscopic observation showed that the cells were being physically destroyed by bacterial predators in the soil. Two of these predators were responsible for the initial, main attack, and they were isolated. The isolates on laboratory media lysed M. luteus cells in a manner similar to the attacks that occurred in soil. Neither predator was obligate, however, nor were they nutritionally fastidious. One of these bacteria produced mycelium and conidia. Under nutritionally poor conditions it used slender filaments of mycelium to seek out host cells. It had at least some of the characteristics of a Streptoverticillium species. The other bacterium was a short, gram-negative rod that did not easily fit into any of the known groups of gram-negative bacteria. It attached to host cells, but its mechanism of lysing these cells is not known.

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PubMed1980

Myceloid growth of Arthrobacter globiformis and other Arthrobacter species.

Transitory myceloid growth occurs in certain complex media with Arthrobacter globiformis strain ATCC 8010. This type of growth, however, was not observed in a medium which contained an array of metal ions but did not contain agents able to complex metal ions. Addition of metal-complexing agents to this medium caused an interruption in the life cycle of strain 8010 so that growth occurred only as the myceloid form. It appeared that manganese was the critical metal that was removed by the metal-complexing agents. During growth, the myceloid cells started to fragment, but wall septation was incomplete. A. globiformis strain ATCC 4336 and several other Arthrobacter species and soil isolates, but not Arthrobacter crystallopoietes, responded to metal-complexing agents as did strain 8010. Biotin and vitamin B12 were not involved in this myceloid growth.

Arthrobacter↗
PubMed1979

Attachment to autoclaved soil of bacterial cells from pure cultures of soil isolates.

Pure cultures of Arthrobacter globiformis and four fresh soil isolates were incubated individually in autoclaved soil, in both the presence and absence of glucose. These bacteria grew in the soil and, except for A. globiformis, eventually attached firmly to the soil solids. Firmly attached cells were defined as those which could not be separated from the soil solids by blending combined with a series of low-speed centrifugal washings. The attachment attained by the soil isolates appeared to duplicate that of the overall bacterial population that resides naturally in unaltered, unamended soil. Cell attachment in the autoclaved-soil system was accelerated slightly by glucose, but, except for one soil isolate, several months of incubation were still required before firm attachment was complete. Electron microscopy indicated that all attached cells produced extracellular polysaccharide slimes in the autoclaved soil and that these materials appeared to connect the cells to surrounding pieces of soil debris. The actual role of polysaccharides in attachment was not clear, however, because at least one of these organisms possessed extracellular slime during the long period in which it had not yet attached to the soil.

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PubMed1979

Minute tubular forms in soil.

Large numbers of minute, flat, long, straight, but often broken structures were observed in aqueous extracts of soil. We have applied the purely descriptive term 'tubules' to these structure, because they apparently became flattened during preparation for electron-microscopic viewing. The tubules appeared to be composed of parallel fibers held together by protein. Most of the tubules fell within a ranged of 10 to 50 nm in width. Lengths (of broken pieces) ranged from 0.2 to 1 micron or more. A few unbroken ends were found. They were rounded. Tubular structures of similar dimensions were found surrounding lysed cells in sectioned preparations of bacteria that had been separated from soil. The tubules were present in surface soils but not a subsurface sample. Their numbers decreased during bacterial multiplication in soil or broth containing soil. No evidence was found of cleared areas or increase in number of tubules when the tubules were plated with a heterogeneous microbial flora from soil.

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