Ecology of nematophagous fungi: vertical distribution in a deciduous woodland

Summary The distribution of nematophagous fungi in soil collected from a deciduous woodland is compared to various biotic and abiotic soil factors. The microfungi are isolated at all depths down to a maximum of 35 cm. Predators forming constricting rings, adhesive branches and adhesive knobs are restricted to the upper litter and humus layers. The net forming predators and endoparasites are isolated at all depths, although they are significantly more abundant in the lower mineral rich soils. A much greater species diversity of nematophagous fungi is recorded in the upper organic zones.Preliminary soil analysis indicates thatCephalosporium balanoides is independent of all soil variables, while predators able to form traps spontaneously are restricted to the organic soils which are rich in nematodes. Non-spontaneous trap forming predators, which are excellent saprophytes, are isolated from the deeper soils which are low in nutrients. The ecological significance of these results is discussed.     

Metabolic and energetic aspects of the growth of Clostridium butyricum on glucose in chemostat culture

The influence of a number of environmental parameters on the fermentation of glucose, and on the energetics of growth of Clostridium butyricum in chemostat culture, have been studied. With cultures that were continuously sparged with nitrogen gas, glucose was fermented primarily to acetate and butyrate with a fixed stoichiometry. Thus, irrespective of the growth rate, input glucose concentration specific nutrient limitation and, within limits, the culture pH value, the acetate/butyrate molar ratio in the culture extracellular fluids was uniformly 0.74±0.07. Thus, the efficiency with which ATP was generated from glucose catabolism also was constant at 3.27±0.02 mol ATP/mol glucose fermented. However, the rate of glucose fermentation at a fixed growth rate, and hence the rate of ATP generation, varied markedly under some conditions leading to changes in the Y _glucose and Y _ATP values. In general, glucose-sufficient cultures expressed lower yield values than a correponding glucose-limited culture, and this was particularly marked with a potassium-limited culture. However, with a glucose-limited culture increasing the input glucose concentration above 40g glucose·l^-1 also led to a significant decrease in the yield values that could be partially reversed by increasing the sparging rate of the nitrogen gas. Finally glucose-limited cultures immediately expressed an increased rate of glucose fermentation when relieved of their growth limitation. Since the rate of cell synthesis did not increase instantaneously, again the yield values with respect to glucose consumed and ATP generated transiently decreased.Two conditions were found to effect a change in the fermentation pattern with a lowering of the acetate/butyrate molar ratio. First, a significant decrease in this ratio was observed when a glucose-limited culture was not sparged with nitrogen gas; and second, a substantial (and progressive) decrease was observed to follow addition of increasing amounts of mannitol to a glucose-limited culture. In both cases, however, there was no apparent change in the Y _ATP value.These results are discussed with respect to two imponder-ables, namely the mechanism(s) by which C. butyricum might partially or totally dissociate catabolism from anabolism, and how it might dispose of the excess reductant [as NAD(P)H] that attends both the formation of acetate from glucose and the fermentation of mannitol. With regards to the latter, evidence is presented that supports the conclusion that the ferredoxin-mediated oxidation of NAD(P)H, generating H₂, is neither coupled to, nor driven by, an energy-yielding reaction.     

Lactic acid production from whey permeate by immobilized Lactobacillus casei

Two matrices have been assessed for their ability to immobilize Lactobacillus casei cells for lactic acid fermentation in whey permeate medium. Agar at 2% concentration was found to be a better gel than polyacrylamide in its effectiveness to entrap the bacterial cells to carry out batch fermentation up to three repeat runs. Of the various physiological parameters studied, temperature and pH were observed to have no significant influence on the fermentation ability of the immobilized organism. A temperature range of 40–50°C and a pH range of 4.5–6.0 rather than specific values, were found to be optimum when fermentation was carried out under stationary conditions. In batch fermentation ～90% conversion of the substrate (lactose) was achieved in 48 h using immobilized cell gel cubes of 4 × 2 × 2 mm size, containing 400 mg dry bacterial cells per flask and 4.5% w/v (initial) whey lactose content as substrate. However, further increase in substrate levels tested (>4.5% w/v) did not improve the process efficiency. Supplementation of Mg²⁺ (1 mM) and agricultural by-products (mustard oil cake, 6%) in the whey permeate medium further improved the acid production ability of the immobilized cells under study.     

The isolation and restriction mapping of a miniplasmid from the Actinomycete Nocardia corallina

Abstract A variety of plasmids has been identified as covalently closed circular and linear DNA in certain Actinomycetes, such as Streptomyces . This paper describes the first isolation and characterisation of a plasmid from the genus Nocardia . The plasmid pKU100 isolated from Nocardia corallina is a cccDNA molecule, 2.7 kb in length. This plasmid has been mapped with a wide variety of restriction enzymes and contains a number of unique restriction sites making it suitable for development as a cloning vector.     

Anaerobic degradation of 3,4,5-trimethoxybenzoate by a defined mixed culture of Acetobacterium woodii, Pelobacter acidigallici, and Desulfobacter postgatei

Abstract Acetobacterium woodii was continuously grown on 3,4,5-trimethoxybenzoate as pure culture or in commensalistic combination with Pelobacter acidigallici and Desulfobacter postgatei . Under pure culture conditions the following growth parameters were determined: μ _max= 0.112 h⁻¹, K _s= 1.07 mM, Y _max= 35 g/mol, and m = 0.22 mmol·g⁻¹·h⁻¹. In coculture with P. acidigallici the affinity for the substrate increased and the K _s value was found to be 135 μM. Under batch culture conditions mixed populations of A. woodii, P. acidigallici , and D. postgatei completely mineralized 3,4,5-trimethoxybenzoate to CO₂, whereas under continuous culture conditions more than 3 mM acetate remained unused.     

Induction of acetoacetate decarboxylase in Clostridium acetobutylicum

Abstract Factors that may initiate the biosynthesis of acetoacetate decarboxylase were investigated in resting cells of Clostridium acetobutylicum . Linear acids from C₁ to C₄ were inducers, whereas branched acids and linear acids from C₅ to C₇ were not inducers of acetoacetate decarboxylase biosynthesis. Induction of acetoacetate decarboxylase was maximal at pH 4.8 in the presence of acid concentrations comparable with those found during fermentation. In growth conditions repression of acetoacetate decarboxylase biosynthesis was found. This fact explains that acetone production by Clostridium acetobutylicum occurs when growth slows down.     

Comparison of a Thermoanaerobium sp. from a New Zealand hot spring with Thermoanaerobium brockii

Abstract An anaerobic ethanologenic strain of extremely thermophilic bacteria isolated from a New Zealand hot spring resembled Thermoanaerobium brockii in morphology and cell-wall ultrastructure. However, antibodies produced against the New Zealand isolate did not crossreact with the type strain of T. brockii . The New Zealand isolate strain Tok6-B1 fermented a wider range of carbohydrate substrates, including pentoses, and was less inhibited by a hydrogen atmosphere. Ethanol and acetate were major end-products and lactate a minor product of glucose fermentation. Under a hydrogen atmosphere, these 3 end-products were formed in approximately equal amounts.     

Nematicides and Nonconventional Soil Amendments in the Management of Root-Knot Nematode on Cotton

Granular and liquid commercial humates, with micronutrients, and a microbial fermentation product were compared in several combinations with nematicides for their effects on cotton lint yield and root-knot nematode suppression. Fumigant nematicides effectively reduced cotton root galling caused by root-knot nematodes, and cotton lint yields increased. Organophosphates and carbamates were not effective. Occasionally, cotton lint yields were increased or maintained with combination treatments o f humates, micronutrients, and a microbial fermentation product, but galling o f cotton roots by root-knot nematodes was usually not reduced by these treatments.     

Phytase production byAspergillus ficuum on semisolid substrate

Summary Phytase production byAspergillus ficuum was studied using solid state cultivation on several cereal grains and legume seeds. The microbial phytase was used to hydrolyze the phytate in soybean meal and cotton seed meal. Wheat bran, soybean meal, cottonseed meal and corn meal supported good fungal growth and yielded a high level of phytase when an adequate amount of moisture was present. The level of phytase production on solid substrate was higher than that obtained by submerged liquid fermentation. Higher levels of phosphorus (more than 10 mg Pi/100 g substrate) in the growth medium (static culture) inhibited phytase synthesis, and the degree of phosphorus inhibition was less apparent in semisolid medium than in liquid medium. A static cultivation on semisolid substrate produced a higher level of phytase (2-20-fold) than that obtained by agitated cultivation. The minimal amount of water required for growth and enzyme production on those substrates was about 15%, while the optimum level for phytase production was between 25 and 35% and that for cell growth was above 50%. Optimum pH for phytase production was between 4 and 6.A ficuum grew well on raw (unheated) substrate containing a minimal amount of water and produced as much phytase as on heated substrate. About half of the phytic acid in soybean meal and cottonseed meal was hydrolyzed by treatment withA. ficuum phytase.