Growth of Physarum flavicomum and Physarum rigidum in chemically defined minimal media

The life cycles of two species of Myxomycetes in Physarales, Physarum rigidum and Didymium squamulosum

Myxomycetes are eukaryotic microorganisms containing characteristics akin to both fungi and amoebae. They can complete their whole life cycles while being cultured on agar media, and under-laboratory conditions, which favors taxonomic, phylogenetic, and cytological researches. Here, we describe the life cycles of two such species: Didymium squamulosum collected from the field and Physarum rigidum cultured from moist chamber both belonging to the Order Physarales. Three per cent oat-agar media (OAM) was used to culture the plasmodia until they aggregated and were almost starved. Natural light was then applied to the plasmodia to induce fructification. Their life cycles share the same common stages, namely: spore, myxamoebae, swarm cell, plasmodia, and sporulation. In this study, we describe the morphogenesis from spore to spore of two species by differential interference contrast (DIC) and stereoscopic microscopies, as well as discuss the differences between the development of both species and interspecies. We found that the spore germination method of both species was the same. However, there were differences noted in time taken and fruiting body formation. Unlike P. rigidum, the species D. squamulosum did not require natural light stimulation. Moreover, the maturation process of both species had similar color transitions but exhibited distinct morphology in each developmental stage except during the swarm cell stage.

Chemically defined media for the cultivation of Naegleria: pathogenic and high temperature tolerant species

Chemically defined minimal media for the cultivation of high temperature tolerant and pathogenic Naegleria spp. have been developed. A defined minimal medium, identical for N. fowleri and N. lovaniensis, consists of eleven amino acids (arginine, glycine, histidine, isoleucine, leucine, methionine, phenylalanine, proline, threonine, tryptophan, and valine), six vitamins (biotin, folic acid, hemin, pyridoxal, riboflavin, and thiamine), guanosine, glucose, salts, and metals. Three of the four strains of Naegleria fowleri tested (ATCC 30100, ATCC 30863, and ATCC 30896) and two strains of N. lovaniensis (ATCC 30467 and ATCC 30569) could be cultured beyond ten subcultures on this medium. For N. fowleri ATCC 30894 diaminopimelic acid, or lysine, or glutamic acid was also required. Mean generation time was reduced and population density increased for all strains with the introduction of glutamic acid. Glucose could be eliminated from the minimal medium only if glutamic acid was present. Without glucose, mean generation time increased and population density decreased. Diaminopimelic acid could substitute for lysin for ATCC 30894, indicating that Naegleria species may synthesize their lysine via the DAP pathway. Naegleria fowleri ATCC 30100 could be adapted to grow without serine or glycine in the minimal medium with glutamic acid added, but with mean generation time increased and population density decreased. The strain could be grown in the minimal medium in the absence of metals. For growth of N. australiensis ATCC 30958, modification of the medium by increasing metals ten-fold, substituting guanine for guanosine and adding lysine, glutamic acid, and six vitamins (p-aminobenzoic acid, choline chloride, inositol, vitamin B12, nicotinamide, and Ca pantothenate) was required.

Growth of the haploid phase of the myxomycete Physarum flavicomum in defined minimal medium

The haploid phase (myxamoebae-swarm cells) of the myxomycete Physarum flavicomum grew readily in chemical defined liquid media. The minimal medium contained salts, glucose, biotin, thiamine, hematin, glycine, L-arginine and L-methionine. Cell yields of 1.4 times 10(7) cells/ml were obtained in this medium in aerobic shake culture. These cells consumed about 35 muliters of oxygen/mg protein-hr in the minimal medium. The morphology of cells maintained in this medium appeared to be "normal". L-valine replaced either glycine or L-methionine in the minimal medium but the growth rates and cell yields were reduced. Growth rates increased in media containing four, seven, or fourteen amino acids.

Purification and properties of cytoplasmic and mitochondrial malate dehydrogenases of Physarum polycephalum

Two isoenzymes of malate dehydrogenase (MDH) were demonstrated in plasmodia of Physarum polycephalum by polyacrylamide-gel electrophoresis. The more "cathodal" form was uniquely associated with mitochondria (M-MDH) and the other form was found in the soluble cytoplasm (S-MDH). The isoenzymes were separated by acetone fractionation of soluble plasmodial homogenates acidified to pH 5.0. The M-MDH was purified 201-fold by cetylpyridinium chloride treatment, fractionation with ammonium sulfate, gradient elution from sulfoethyl cellulose at pH 6.0, and Sephadex G-100 chromatography. The S-MDH was purified 155-fold by ammonium sulfate fractionation, diethylaminoethyl cellulose chromatography, gradient elution from sulfoethyl cellulose at pH 5.5, and Sephadex G-100 chromatography. The optimal cis-oxalacetate concentrations were 0.35 mM for M-MDH and 0.25 mM for S-MDH, and the optimal pH for both isoenzymes was 7.6 for oxalacetate reduction. The optimal l-malate concentrations were 5 mM for S-MDH and 6 mM for M-MDH, and both isoenzymes exhibited an optimal pH of 10.0 for L-malate oxidation. The Michaelis constants of S-MDH and M-MDH served to discriminate between the isoenzymes. The S-MDH was more heat-stable than the M-MDH. High concentrations of oxalacetate and malate inhibited S-MDH more than M-MDH. The isoenzymes were further distinguished by their utilization of analogues of nicotinamide adenine dinucleotide. Many properties of the Physarum isoenzymes were similar to those of more complex organisms, especially vertebrates.