The colonization of land by plants appears to have coincided with the appearance of mycorrhiza-like fungi. Over evolutionary time, fungi have maintained their prominent role in the formation of mycorrhizal associations. In addition, however, they have been able to occupy other terrestrial niches of which the decomposition of recalcitrant organic matter is perhaps the most remarkable. This implies that, in contrast to that of aquatic organic matter decomposition, bacteria have not been able to monopolize decomposition processes in terrestrial ecosystems. The emergence of fungi in terrestrial ecosystems must have had a strong impact on the evolution of terrestrial bacteria. On the one hand, potential decomposition niches, e.g. lignin degradation, have been lost for bacteria, whereas on the other hand the presence of fungi has itself created new bacterial niches. Confrontation between bacteria and fungi is ongoing, and from studying contemporary interactions, we can learn about the impact that fungi presently have, and have had in the past, on the ecology and evolution of terrestrial bacteria. In the first part of this review, the focus is on niche differentiation between soil bacteria and fungi involved in the decomposition of plant-derived organic matter. Bacteria and fungi are seen to compete for simple plant-derived substrates and have developed antagonistic strategies. For more recalcitrant organic substrates, e.g. cellulose and lignin, both competitive and mutualistic strategies appear to have evolved. In the second part of the review, bacterial niches with respect to the utilization of fungal-derived substrates are considered. Here, several lines of development can be recognized, ranging from mutualistic exudate-consuming bacteria that are associated with fungal surfaces to endosymbiotic and mycophagous bacteria. In some cases, there are indications of fungal specific selection in fungus-associated bacteria, and possible mechanisms for such selection are discussed.

Living in a fungal world: impact of fungi on soil bacterial niche development⋆

http://science.sciencemag.org/content/sci/171/3973/757.full.pdf

Allelochemics: Chemical Interactions between Species

https://www.cell.com/molecular-cell/pdf/S1097-2765(05)00089-4.pdf

Structural Determinants of Phosphoinositide 3-kinase Inhibition by Wortmannin, LY294002, Quercetin, Myricetin, and Staurosporine

Isolates from different species-groups of Trichoderma were tested for production of non-volatile antibiotics, by an agar layer technique. Preliminary studies on the chemical nature of these antibiotics were made. Many isolates produced non-volatile antibiotics active against a range of fungi. The ability to produce such antibiotics varied between isolates of the same species-group as well as between isolates of different species groups. The susceptibility of fungi to these antibiotics varied widely; Fomes annosus (Fr.) Cooke was the most susceptible and Fusarium oxysporum Schlecht, ex Fr. the most resistant of the test fungi used. Gliotoxin and viridin were not produced, but other chloroform-soluble antibiotics, including trichodermin and peptide antibiotics were detected.

Antagonistic properties of species-groups of Trichoderma: II. Production of volatile antibiotics

The transformations of nitrogenous compounds by soil bacteria have beenstudied for over a century. In terms of the global fluxes between aerial and terrestrial-aquatic systems, the simplified nitrogen cycle can be envisioned as a triangle where the only biologically reversible reaction occurs between ammonium and nitrate. The reverse reactions of dinitrogen fixation or denitrification by biological means do not occur in nature. Hence, the reductive process of denitrification, defined as the reduction of nitrate or nitrite to gaseous nitrogen (usually N2), is intimately associated with the oxidative process of nitrification.

Biochemical Ecology of Nitrification and Denitrification

The Effect of Gibberellic Acid on Shoot Growth of Pea Seedlings

With one Figure in the Text Received 6 May i960 SUMMARY Culture filtrates of several strains of Fusarium equiseti (Corda) Sacc. were found to be highly phytotoxic. Several phytotoxic substances were isolated; the most important of these was a colourless crystalline compound, diacetoxyscirpenol, m.p. 161-2°, C19H3607. Though highly phytotoxic in many respects, it markedly stimulates elongation of cress roots at o-oi-o-s /xg./ml. This is not an anti-auxin effect. Diacetoxyscirpenol is at most only slightly inhibitory to fungi and bacteria, but is highly toxic to rats. Two minor metabolic products, m.p. 135-6° and 185-8° respectively, are also described. They, too, were highly phytotoxic, though their spectra of activity were somewhat different from that of diacetoxyscirpenol. They also were highly toxic to rats. Production of these substances is probably not important in the aetiology of disease symptoms in plants parasitized by F. equiseti, but may be significant in cases of toxicosis of animals fed with grain infected by Fusaria. Scirpentriol, a hydrolysis product of diacetoxyscirpenol, is much less phytotoxic but of equal toxicity to rats.

Phytotoxic Compounds produced by Fusarium equiseti

Gibberellic acid is a metabolic product of the fungus Gibberella fujikuroi, similar in physiological properties to the gibberellins described by Japanese investigators. Supplied in a nutrient solution to wheat plants growing in water culture, it causes increased growth of the shoots, as a result of increased length of stem internodes and leaves. The leaves are narrower and paler than those of untreated plants. Under similar conditions pea seedlings develop much elongated stem internodes, but the leaves are little changed in size. These morphological responses are similar to those seen in etiolation.

The total dry weight of both peas and wheat so treated is increased; if shoots alone are considered the increase in dry weight is even greater; the dry weight of roots is reduced, though this does not occur if the gibberellic acid is applied to the shoots in a lanolin paste. The increased dry weight is mainly attributable to increased carbon assimilation. Treated plants contain more soluble carbohydrate than controls, but this accounts only for a small part of the increased carbon assimilation. The increase in glucose content is particularly striking.

Gibberellic acid is rapidly biologically degraded in soil.

The plant‐growth‐promoting properties of gibberellic acid, a metabolic product of the fungus gibberella fujikuroi

Summary Strains of Penicillium Janczewskii Zal. are shown to produce a substance, when grown on synthetic liquid culture media, which causes an unusual stunting and distortion of the germ-tubes and hyphae of Botrytis Allii and other fungi. This substance, known as ‘curling factor’, is produced more abundantly in media containing nitrogen as nitrate than in media containing nitrogen as ammonium salts or peptone. The optimum concentration of glucose in the media is 7·5%, which is noticeably better than 5·0%. Increase in glucose concentration to 10·0% or higher gives no further advantage. The ‘curling factor’ may be removed from active culture-filtrates by extraction with chloroform, ether or n -butyl alcohol or by treatment with activated charcoal followed by elution of the charcoal with ether or chloroform. By extraction with chloroform followed by successive crystallization from ethyl alcohol and dioxan/water mixtures, ‘curling factor’ has been obtained in pure form as colourless crystals. Yields of 150 mg./l. of culture filtrate can be obtained. In concentrations of 25μg./ml., ‘curling factor’ causes the production of short stunted germ-tubes by Botrytis Allii , whose development ceases at an early stage ; lower concentrations (1·0 μg./ml.) cause excessive branching and distortion and lower concentrations still (0·2 μg./ml.) cause a waving of the hyphae. It is characteristic of the substance that relatively high concentrations (100 μg./ml.) do not prevent germination of B. Allii conidia, though far lower concentrations cause the profound physiological effects described.

H. G. Hemming

Papers

The Effect of Gibberellic Acid on Shoot Growth of Pea Seedlings

Phytotoxic Compounds produced by Fusarium equiseti

The plant‐growth‐promoting properties of gibberellic acid, a metabolic product of the fungus gibberella fujikuroi

A substance causing abnormal development of fungal hyphae produced by Penicillium janczewskii zal.

A Physiological Comparison of Gibberellic Acid with Some Auxins