- Volume 42, Issue 2, 1966

SUMMARY: The genus Mallomonopsis (Chrysomonadales) is discussed and five taxa are described from observations with the electron microscope: M. elliptica, M. elliptica var. salina, M. elliptica var. oviformis (formerly Mallomonas oviformis), M. peroneides sp.nov. and M. ouradion (formerly Mallomonas ouradion). The two flagella, which distinguish Mallomonopsis from Mallomonas, comprise a stout one with mastigonemes and a slender one which is smooth and has a photoceptor at its base. The silica scales are compared in detail and are shown to differ in construction as well as in appearance in the different species and are considered to provide the only satisfactory basis for specific separation.

SUMMARY: Strains of Lactobacillus casei and Proteus vulgaris resistant to small molecule inhibitors of dihydrofolate reductase were isolated under various nutritional conditions. When thymine and/or purines were available in the media, several of the isolated strains had nutritional requirements for these metabolites, but resistant lines could still be isolated in their absence. Thus, the biochemical alteration accompanying resistance could be predetermined to a major extent by the design of the experiment.

The wild-type strain of Proteus vulgaris did not incorporate exogenous thymine, and was insensitive to thymine antagonists, while the thymine-requiring strain was highly sensitive to 5-bromouracil, dithiothymine and 2-thiothymine. This suggested that resistance was accompanied by the appearance of a permeability or transport system for thymine.

SUMMARY: Strains of Lactobacillus casei and Proteus vulgaris resistant to small molecule inhibitors of dihydrofolate reductase were isolated under various nutritional conditions. When thymine and/or purines were available in the media, several of the isolated strains had nutritional requirements for these metabolites, but resistant lines could still be isolated in their absence. Thus, the biochemical alteration accompanying resistance could be predetermined to a major extent by the design of the experiment.

The wild-type strain of Proteus vulgaris did not incorporate exogenous thymine, and was insensitive to thymine antagonists, while the thymine-requiring strain was highly sensitive to 5-bromouracil, dithiothymine and 2-thiothymine. This suggested that resistance was accompanied by the appearance of a permeability or transport system for thymine.

SUMMARY: Nocardia opaca, a flavobacterium and certain other bacteria, when grown on o-nitrobenzoate, accumulated anthranilate in the medium in the early stages of growth. The subsequent disappearance of this metabolite in growing cultures was always correlated with the appearance of an anthranilate oxidase system in the organisms. This phenomenon has the features of a typical enzyme adaptation except that the inducer is a by-product of the cells’ own metabolism; hence it has been termed ‘metabolite induction’. The results confirm previous suggestions that, in these micro-organisms, anthranilate is not an obligatory intermediate in the direct energy-producing pathway of o-nitrobenzoate breakdown but is produced in a side reaction.

SUMMARY: Nocardia opaca, a flavobacterium and certain other bacteria, when grown on o-nitrobenzoate, accumulated anthranilate in the medium in the early stages of growth. The subsequent disappearance of this metabolite in growing cultures was always correlated with the appearance of an anthranilate oxidase system in the organisms. This phenomenon has the features of a typical enzyme adaptation except that the inducer is a by-product of the cells’ own metabolism; hence it has been termed ‘metabolite induction’. The results confirm previous suggestions that, in these micro-organisms, anthranilate is not an obligatory intermediate in the direct energy-producing pathway of o-nitrobenzoate breakdown but is produced in a side reaction.

SUMMARY: Anthranilic and o-nitrobenzoic acids act as mutual inhibitors of both growth and substrate oxidation for Nocardia opaca and a flavobacterium which can utilize either substance as sole source of carbon, nitrogen and energy. Growth of the former bacterium on anthranilate induced, apparently simultaneously, both the transport system for anthranilate uptake and the enzymic mechanism necessary for its complete oxidation to CO2 and NH3. Among the enzymes induced by anthranilate was the complete sequence that oxidizes catechol to β-oxoadipate; this was absent from organisms grown in fumarate or glucose media. The properties of the first enzyme in this sequence, a catechol-1, 2-oxygenase, differ in several features from those of the same enzyme induced in this bacterium by growth on o-nitrobenzoic acid.

SUMMARY: Anthranilic and o-nitrobenzoic acids act as mutual inhibitors of both growth and substrate oxidation for Nocardia opaca and a flavobacterium which can utilize either substance as sole source of carbon, nitrogen and energy. Growth of the former bacterium on anthranilate induced, apparently simultaneously, both the transport system for anthranilate uptake and the enzymic mechanism necessary for its complete oxidation to CO2 and NH3. Among the enzymes induced by anthranilate was the complete sequence that oxidizes catechol to β-oxoadipate; this was absent from organisms grown in fumarate or glucose media. The properties of the first enzyme in this sequence, a catechol-1, 2-oxygenase, differ in several features from those of the same enzyme induced in this bacterium by growth on o-nitrobenzoic acid.

SUMMARY: Carbon and nitrogen sources were found to be necessary both for the germination and the associated swelling of the macroconidia of Fusarium culmorum. The swelling of the spores took place before the emergence of the germ tube and was measured by two methods. The spores were shown to have a mucilaginous covering, which affected the uptake of nutrients and into which glucose was absorbed by a physical process rather than by an enzymic one. Tritiated water was used to demonstrate that the swelling of the spores in the presence of a nitrogen source was due largely to water uptake and only in a small part to an increase in dry weight.

SUMMARY: Carbon and nitrogen sources were found to be necessary both for the germination and the associated swelling of the macroconidia of Fusarium culmorum. The swelling of the spores took place before the emergence of the germ tube and was measured by two methods. The spores were shown to have a mucilaginous covering, which affected the uptake of nutrients and into which glucose was absorbed by a physical process rather than by an enzymic one. Tritiated water was used to demonstrate that the swelling of the spores in the presence of a nitrogen source was due largely to water uptake and only in a small part to an increase in dry weight.

SUMMARY: Exposure of cysts of Naegleria gruberi to slightly increased environmental CO2 caused excystement. Excystment was also induced by addition of proline or by an increase in the cyst population density, but both did so by increasing the amount of CO2 produced by the bacteria (Aerobacter aerogenes) which contaminated the cyst suspensions. Molecular CO2 would seem to be an excellent signal to induce excystment of a phagotrophic soil amoeba since the presence of CO2 would indicate an environment favourable for growth of the amoebae. Once excystment is initiated, it can proceed to completion in atmospheric CO2.

SUMMARY: Exposure of cysts of Naegleria gruberi to slightly increased environmental CO2 caused excystement. Excystment was also induced by addition of proline or by an increase in the cyst population density, but both did so by increasing the amount of CO2 produced by the bacteria (Aerobacter aerogenes) which contaminated the cyst suspensions. Molecular CO2 would seem to be an excellent signal to induce excystment of a phagotrophic soil amoeba since the presence of CO2 would indicate an environment favourable for growth of the amoebae. Once excystment is initiated, it can proceed to completion in atmospheric CO2.

SUMMARY: Investigations of the ecology of Saprolegniaceae rely on satisfactory sampling methods. Existing procedures have been considered and new techniques, including a method for the estimation of propagule numbers, are presented. This paper shows the diversity of the communities which may exist in an area of less than 1 km.2; further evidence has been provided on the constancy of these communities. From previous work distribution patterns of a mosaic type were expected; the present results suggest that several orders of such patterns exist, ranging from those within a core of soil about 5 cm. in diameter, through those of quadrats of 1 m.2, to the production of a continuum several metres or even 100 m. in extent.

SUMMARY: Investigations of the ecology of Saprolegniaceae rely on satisfactory sampling methods. Existing procedures have been considered and new techniques, including a method for the estimation of propagule numbers, are presented. This paper shows the diversity of the communities which may exist in an area of less than 1 km.2; further evidence has been provided on the constancy of these communities. From previous work distribution patterns of a mosaic type were expected; the present results suggest that several orders of such patterns exist, ranging from those within a core of soil about 5 cm. in diameter, through those of quadrats of 1 m.2, to the production of a continuum several metres or even 100 m. in extent.

SUMMARY: Although sporangiospores of Rhizopus arrhizus do not swell or produce germ-tubes in distilled water, when they are suspended in heavy water the water in the spore is exchanged with heavy water in the medium. Spores swell and some produce germ-tubes in a glucose solution. Maximum germination occurred in the presence of utilizable carbon and nitrogen sources and suitable compounds containing phosphate, sulphate, potassium and magnesium ions. Germination was accompanied by a considerable increase in oxygen uptake and by the time the germ-tube emerged, the dry weight had increased by about 500%. Respiratory inhibitors (2,4-dinitrophenol, sodium azide, potassium cyanide) inhibited germination; sodium azide inhibited both the oxygen uptake and the dry weight increase.

Electron microscope studies showed structural changes in germinating Rhizopus arrhizus spores similar to those reported in other Rhizopus species: a new inner wall layer was formed, and changes in form and probably number of mitochondria occur. The effects of either anaerobic conditions or media containing sodium azide, on fine structure of germinating R. arrhizus spores were similar; mitochondrial multiplication ceases, mitochondrial cristae became a disorganized collection of undulating ‘plates’, and the nuclear membrane became split in places, thus giving rise to small vacuoles between the two electron-dense layers of the membrane.

SUMMARY: Although sporangiospores of Rhizopus arrhizus do not swell or produce germ-tubes in distilled water, when they are suspended in heavy water the water in the spore is exchanged with heavy water in the medium. Spores swell and some produce germ-tubes in a glucose solution. Maximum germination occurred in the presence of utilizable carbon and nitrogen sources and suitable compounds containing phosphate, sulphate, potassium and magnesium ions. Germination was accompanied by a considerable increase in oxygen uptake and by the time the germ-tube emerged, the dry weight had increased by about 500%. Respiratory inhibitors (2,4-dinitrophenol, sodium azide, potassium cyanide) inhibited germination; sodium azide inhibited both the oxygen uptake and the dry weight increase.

Electron microscope studies showed structural changes in germinating Rhizopus arrhizus spores similar to those reported in other Rhizopus species: a new inner wall layer was formed, and changes in form and probably number of mitochondria occur. The effects of either anaerobic conditions or media containing sodium azide, on fine structure of germinating R. arrhizus spores were similar; mitochondrial multiplication ceases, mitochondrial cristae became a disorganized collection of undulating ‘plates’, and the nuclear membrane became split in places, thus giving rise to small vacuoles between the two electron-dense layers of the membrane.