Ivan L. Roth

Scanning electron microscope studies on ascospores of homothallic species of Neurospora.

The surface and subsurface topography of ascospores of homothallic species of Neurospora has been studied with the scanning electron microscope. Rib surfaces of the ascospore walls, as viewed under SEM, are smooth and free of any fibrillar pattern. Intercostal veins are revealed as pitted furrows in the perisporium aligned with circular to elongate depressions. Height of ribs, depth and continuity of the veins, and distinctiveness of the pitting of the ascospore walls vary according to species. Topographic features of the walls of N. dodgei are the most prominent and those of N. lineolata -are the least prominent. Surface features of the three other homothallic species fall within these two extremes. SEM views of ascospores after removal of the perisporium show that the germinal pore is an opening in the episporium and that the perisporium is not perforated.

Observations on the peridial platelets of Clastoderma debaryanum

The relationship of sporangial platelets to the peridium and capillitium of Clastoderma debaryanum was studied with scanning electron microscopy. Results indicated that platelets do not represent peridial remnants that adhere to tips of capillitial branches. Instead, they are flattened, membranous structures that are in continuity with ends of capillitial branches. The thin fragile peridium, which initially envelopes the sporangial head, disappears completely from mature sporangia except for a collar-like remnant at the top of the stalk.

Published Inconsistencies in Methyl Red and Voges-Proskauer Reactions of Klebsiella pneumoniae

Inconsistencies in the results of methyl red and Voges-Proskauer tests of Klebsiella pneumoniae have been published. These inconsistencies result from the unresolved taxonomic position of K. aerogenes.

Ultrastructure of the capsule of Klebsiella pneumoniae and slime of Enterobacter aerogenes revealed by freeze etching

SummaryThe capsule of Klebsiella pneumoniae type I and slime of Enterobacter aerogenes strain A3 (SL) was examined by electron microscopy using the freeze etch technique. The capsules of K. pneumoniae were found to be composed of several layers of polysaccharide 10 nm thick; while the polysaccharide slime of E. aerogenes strain A3 (SL) was found to be composed of a diffuse network of fibrils. This work represents the first effort to visualize the replica of the unfixed, partially hydrated bacterial capsule or slime in the electron microscope. The slime of E. aerogenes strain A3 (SL) which was purified, and then freeze etched, resembled the layered structure of the capsule of K. pneumoniae. It is suggested that the charge or dielectric constant of the slime polysaccharide polymers was altered during purification, thereby permitting the layering to occur.

SEM STUDIES ON OPERCULUM STRUCTURE IN THE MYXOMYCETE TRICHIA CRATERIFORMIS

Scanning electron microscope studies have been conducted on the operculum of sporangia of Trichia crateriformis and its structure has been compared with that of other operculate Myxomycetes. The operculum of T. crateriformis consists of a single layer of sporelike bodies that have cell walls ornamented with warty excresences similar to those of the spores. It adjoins the membranous peridium of the sporangium in a transition region which constitutes the dehiscence zone. In other taxa with operculate sporophores examined the operculum is membranous and has a structure generally similar to that of its associated peridium. The type of operculum in T. crateriformis may be unique for the Myxomycetes. Several species of Myxomycetes form sporangia furnished with a well-defined operculum. Species exhibiting this characteristic are Metatrichia vesparium (Batsch) Nann-Brem., certain species of Craterium and Licea, Perichaena depressa Libert, and Trichia crateriformis Martin. During the course of some scanning electron microscope (SEM) studies of types of authenticated specimens of taxa in the Trichiaceae, we observed that the operculum of the sporangium of T. crateriformis is strikingly different in structure from that of its contiguous peridial wall. The T. crateriformis operculum was noted to consist of discrete spore-like units with ornamented wall surfaces similar to those of the spores. A report on this apparently unique type of operculum structure is presented in this communication.

Trichia fernbankensis sp. nov., a second species of Trichia with operculate sporangia

A new species, Trichia fernbankensis , with operculate sporangia is described and illustrated. It differs from the most closely related taxon, T. crateriformis , principally by the reticulate spores and non-cellular operculum.