Abstract Not Available.

Abstract Not Available.

Since the tapeworm, Hymenolepis diminuta, and the acanthocephalan, Moniliformis dubius, are thought to obtain all their nutrients by absorption through the body surface, are known to inhabit the same general part of the rat intestine, and require carbohydrate from host ingesta for growth and reproduction, competition for nutrients and/or specific habitat sites should be demonstrable in this host-parasite-parasite system. This may be important as a factor in the regulation of the distribution and abundance of endoparasitic helminths. A study was therefore undertaken to investigate the interactions, especially the possibility of competition, between H. diminuta and M. dubius in the rat. More specifically, the study has three aims: (1) To study the effects of concurrent infection on H. diminuta and M. dubius . (2) To determine whether the effects demonstrated are due to the production (by one or both of the helminths) of toxic metabolic products, to changes in host physiology in response to the presence of one or both of the helminths, to competition for space, or to competition for some essential metabolite(s) that is (are) relatively scarce in the intestine. (3) To determine the physiological basis for the effects demonstrated.

Abstract Not Available.

Abstract Not Available.

This study was initially undertaken to determine whether the role of phosphorus in the carbohydrate metabolism of tapeworms is similar to or different from the role of this element in the chemical economy of other animals. A study was also made of the overall carbohydrate utilization as indicated by some of the end products, and of some aspects of the electron transfer mechanism at the "terminal end" of the carbohydrate metabolism.

Identifying benefits to cooperation is important in studying social evolution. When the social amoebae of Dictyostelium discoideum starve, they aggregate to form multicellular slugs that migrate towards the soil surface to form fruiting bodies. Multicellularity in D. discoideum is thought to help provide protection from predators and aid in the dispersal of reproductive spores. Here we show an additional benefit of local dispersal. Utilizing D. discoideum's phototactic behavior, we induced slug migration over bacteria and show that this passage results in the removal of bacteria. Time-lapse video revealed that slugs do not dissociate on contact with bacteria, rather cells sloughed from the migrating slugs consume the prey and reproduce. Using an aggregation mutant, we show that the cells slugs shed are able to reach and colonize food sources solitary amoebae cannot. We propose that the exploitation of local food patches is an important selective benefit favoring multicellularity in D. discoideum .

Complementation studies were carried out with a Clostridium acetobutylicum ATCC 824 plasmid library and Escherichia coli glycolytic mutants. Degenerate primers were designed from homologous regions in known glycolysis genes, and used to screen the selected plasmids. The gene encoding phosphofructokinase and the surrounding DNA was sequenced. The gene encoding pyruvate kinase was discovered downstream of the phosphofructokinase gene. It appears that phosphofructokinase and pyruvate kinase form an operon. The gene encoding glyceraldehyde-3-phosphate dehydrogenase was also found in a cosmid library, but only partially sequenced. Phosphofructokinase from C. acetobutylicum has high homology to the phosphofructokinases from Bacillus stearothermophilus, Bacillus macquarensis, Escherichia coli and other microbes. Conserved residues involved in the binding of substrates, cofactors and allosteric effectors are found in the C. acetobutylicum homologue. The pyruvate kinase/phosphofructokinase operon may act as a "regulatory operon" for glycolysis in C. acetobutylicum.

The rpoS gene encodes a stationary phase specific sigma factor of RNA polymerase and is a key regulator of Escherichia coli's stationary phase responses. It has been observed under laboratory conditions that gene expression is induced by stressful environmental conditions and certain metabolic intermediates. Batch and continuous cultures were employed to investigate the effect of environmental conditions and high reactor acetate levels on the transcriptional activation of the rpoS promotor. In complex media, the rpoS gene was induced in the late exponential phase of batch growth. Chemostat experiments were then conducted in complex media to examine the effects of acetate, glucose, and variations in cell density due to media quality on gene expression. Residula acetate and glucose concentrations were found to modulate rpoS behavior. However, it was observed that under these particular experimental conditions, cell density had no appreciable effect on the transcriptional activation of the rpoS promotor.

The DNA of Bacillus subtilis bacteriophage SP01 is a linear duplex 140 kilobasepairs long, with direct terminal repeats of 12.4 kilobasepairs. It contains the unusual base 5-hydroxymethyluracil in place of thymine. Southern transfer hybridization analysis of pulse-labeled early replicating intermediates was used to localize the origins of replication on the physical map of SP01. The fragments that were consistently detected in this manner correspond to a region of the DNA extending from the middle of the left terminal repeat to about 32 kilobasepairs from the left end of the genome. Thus there is at least one origin of replication between the middle of the left terminal repeat and a point about 32 kilobasepairs from the left end of the genome. However, because of the nature of the terminal repeats and the ambiguity of the restriction maps of this region, as many as three origins of replication may be indicated: one in each direct terminal repeat and one about 30-32 kilobasepairs from the left end of the genome, in the vicinity of Xba I fragment 16b.