Secondary metabolites, including antibiotics, are produced in nature and serve survival functions for the organisms producing them. The antibiotics are a heterogeneous group, the functions of some being related to and others being unrelated to their antimicrobial activities. Secondary metabolites serve: (i) as competitive weapons used against other bacteria, fungi, amoebae, plants, insects, and large animals; (ii) as metal transporting agents; (iii) as agents of symbiosis between microbes and plants, nematodes, insects, and higher animals; (iv) as sexual hormones; and (v) as differentiation effectors. Although antibiotics are not obligatory for sporulation, some secondary metabolites (including antibiotics) stimulate spore formation and inhibit or stimulate germination. Formation of secondary metabolites and spores are regulated by similar factors. This similarity could insure secondary metabolite production during sporulation. Thus the secondary metabolite can: (i) slow down germination of spores until a less competitive environment and more favorable conditions for growth exist; (ii) protect the dormant or initiated spore from consumption by amoebae; or (iii) cleanse the immediate environment of competing microorganisms during germination.

The natural functions of secondary metabolites.

Summary: Sex is shrouded in mystery. Not only does it preferentially occur in the dark for both fungi and many animals, but evolutionary biologists continue to debate its benefits given costs in light of its pervasive nature. Experimental studies of the benefits and costs of sexual reproduction with fungi as model systems have begun to provide evidence that the balance between sexual and asexual reproduction shifts in response to selective pressures. Given their unique evolutionary history as opisthokonts, along with metazoans, fungi serve as exceptional models for the evolution of sex and sex-determining regions of the genome (the mating type locus) and for transitions that commonly occur between outcrossing/self-sterile and inbreeding/self-fertile modes of reproduction. We review here the state of the understanding of sex and its evolution in the fungal kingdom and also areas where the field has contributed and will continue to contribute to illuminating general principles and paradigms of sexual reproduction.

The Evolution of Sex: a Perspective from the Fungal Kingdom

Aromatic azo compounds are ubiquitous motifs and are widely used in industry as organic dyes, indicators, pigments, food additives, radical reaction initiators, and therapeutic agents. Despite numerous efforts towards the synthesis of azo derivatives, big challenges still remain because: 1) the catalytic procedures that have been reported to afford high yields have been less widely explored; 2) stoichiometric and environmentally unfriendly oxidants, such as manganese salts, lead salts, mercury salts, or ferrates were previously employed for their preparation form aromatic amines; 3) unsymmetric aromatic azo compounds are not easy to prepare. Usually, two step syntheses are used, proceeding from anilines via diazonium salt or nitrosobenzene intermediates, using stoichiometric amounts of nitrite salts or other oxidants, to produce unsymmetric aromatic azo compounds, with inorganic salts as the by-products [Eq. (1)].

Copper‐Catalyzed Aerobic Oxidative Dehydrogenative Coupling of Anilines Leading to Aromatic Azo Compounds using Dioxygen as an Oxidant

The ability to produce a wide variety of secondary metabolites and a mycelial form of growth that develops into spores are two biological aspects characteristic of the gram-positive bacterial genus Streptomyces. Secondary metabolism and cell differentiation are controlled by diffusible low-molecular-weight chemical substances called autoregulators. A-factor, the representative of the autoregulators, triggers streptomycin production and aerial-mycelium formation in Streptomyces griseus. A-factor exerts its regulatory function with the aid of a receptor protein that itself acts as a repressor-type regulator. The A-factor signal via the A-factor-receptor protein is transferred to downstream genes, such as streptomycin-production genes and sporulation genes, through multiple regulatory genes in a complex regulatory cascade. Thus, A-factor can be termed a "microbial hormone." This review deals with the A-factor-regulatory cascade as a model system for other autoregulators. The biosynthesis of A-factor, the structures and characteristics of other autoregulators, and the importance of these autoregulators in the ecosystem are also included.

Autoregulatory factors and communication in actinomycetes.

Vicinal C,H spin coupling (3JC,H) in substituted alkenes has been investigated systematically. Emphasis is laid on the stereochemical significance (Jtrans/Jcis) and on the various structural factors which influence 3JC,H, such as π-bond order, torsional angle ϕ, bond angle θ, electronegativity of substituents and steric effects. A new type of γ-effect is observed in 3JtransC,H which appears to have the same origin as the γ-shift effect. By comparison of 3J and 3JH,H, it was found that the relation 3JC,H ≈ 0·6 3JH,H holds for both trans and cis coupling constants. Finally, it is concluded that 3JC,H constitutes a valuable criterion to distinguish E- and Z-isomers, particularly in trisubstituted alkenes. Applications to natural products are presented.

William H. Nutting

Papers

Synthesis and stereochemical assignment of trans-2-methyl-2-pentenoic acid and the corresponding esters, aldehydes, and alcohols

The structure of sirenin

Production, isolation, and characterization of sirenin.

4-(4-Nitrophenylazo)benzoic acid. Improved synthesis of its acid chloride and spectroscopic properties of its esters