Molecular analysis of Gigaspora (Glomales, Gigasporaceae)

This work presents a cooperative effort to integrate new molecular (isozyme and SSU analyses) characters into the morphological taxonomy of the genus Gigaspora (Glomales). Previous analyses of published Gigaspora SSU sequences indicated the presence of a few polymorphic nucleotides in the region delimited by primers NS71-SSU 1492'. In our study, the SSU of 24 isolates of arbuscular mycorrhizal (AM) fungi from the Gigasporaceae were amplified and the NS71-SSU 1492' region was directly sequenced. The corresponding sequences of four more isolates of AM fungi from Gigasporaceae, already published, were also included in our analyses. Three Gigaspora groups were identified on the basis of a 6 nucleotide-long 'molecular signature': Gigaspora rosea group ( G. rosea + G. albida ), Gigaspora margarita group ( G. margarita + G. decipiens ) and Gigaspora gigantea , which constituted a group by itself. The isozyme profiles (malate dehydrogenase, MDH) of 12 of these 28 isolates, and seven other isolates not sequenced, were compared. The results obtained further supported the grouping of isolates provided by the SSU analysis. Both SSU and MDH analysis indicated that two out of the 35 isolates had been misidentified, which was confirmed when their morphology was reassessed. The use of the Gigaspora intrageneric molecular signature as a quick, unambiguous and objective method to recognize Gigaspora isolates under any (field or laboratory) experimental conditions is suggested.     

Antibiotics and the search for new principles

Originally presented as an Invited Lecture at the 1990 Society for Industrial Microbiology Annual Meeting in Orlando, Florida.     

Purification and properties of ATPase inhibitor from rat liver mitochondria

(1) The ATPase inhibitor protein has been isolated from rat liver mitochondria in purified form. The molecular weight determined by sodium dodecyl sulfate gel electrophoresis is approximately 9500, and the isoelectric point is 8.9.

(2) The protein inhibits both the soluble ATPase and the particle-bound ATPase from rat liver mitochondria. It also inhibits ATPase activities of soluble F₁, and inhibitor-depleted submitochondrial particles derived from bovine heart mitochondria.

(3) On particle-bound ATPase the inhibitor has its maximal effect if incubated in the presence of Mg²⁺. ATP at slightly acidic pH.

(4) The inhibitor has a minimal effect on P_i-ATP exchange activity in sonicated submitochondrial particles. However, unexpectedly the inhibitor greatly stimulates P_i-ATP exchange activity in whole mitochondria while the low ATPase activity of the mitochondria is not affected. The possible mechanism of action of the inhibitor on intact mitochondria is offered.     

The effect of transfer from low to high light intensity on electron transport in Rhodospirillum rubrum membranes

The effects of transfer from low to high ligh intensity on membrane bound electrontransport reactions of Rhodospirillum rubrum were investigated. The experiments were performed with cultures which did not form bacteriochlorophyll (Bchl) for about two cell mass doublings during the initial phase of adaptation to high light intensity. Lack of Bchl synthesis causes a decrease of Bchl contents of cells and membranes. Also, the cellular amounts of photosynthetically active intracytoplasmic membranes decrease.In crude membrane fractions containing both cytoplasmic and intracytoplasmic membranes the initial activities of NADH oxidizing reactions increase only slightly (about 1.2 times) per protein, but the initial activities of succinate oxidizing reactions decrease (multiplied by a factor of 0.7). On a Bchl basis activities of NADH oxidizing reactions increase 3.4 times while activities of succinate dependent reactions increase 1.9 times. With isolated intracytoplasmic membranes activities of NADH as well as succinate dependent reactions increase to a comparable extent on a Bchl basis (about 1.8 times) and stay nearly constant on a protein basis. Cytochrome c oxidase responds like succinate dependent reactions. The data indicate that in cells growing under the conditions applied NADH oxidizing electron transport systems are incorporated into both, cytoplasmic and intracytoplasmic membranes, while incorporation of succinate oxidizing systems is confined to intracytoplasmic membranes only.Activities of photophosphorylation and succinate dependent NAD⁺ reduction in the light increase per Bchl about 1.8 times. On a Bchl basis increases of the fast light induced on reactions at 422 nm and increases of soluble cytochrome c ₂ levels are comparable to increases of photophosphorylations and succinate dependent activities. But increases of slow light off reactions at 428 nm and of b-type cytochrome levels become three times greater then increases of cytochrome c ₂ reactions and levels. These results infer that although electrontransport reactions of intracytoplasmic membranes change correlated to each other, Bchl, cytochrome c ₂ and b-type cytochromes cellular levels are independent of each other. Furthermore, the data indicate that cytochrome c ₂ rather than b-type cytochrome is involved with steps rate limiting for photophosphorylation.Abbreviations Bchl bacteriochlorophyll - DCIP 2,6-dichlorophenolindophenol