Chen Jiang

By Yi Jiang, Qinyuan Li, Xiu Chen and Chenglin Jiang

Actinobacteria (actinomycetes) have been received much attention, as these bacteria produce a variety of natural drugs and other bioactive metabolites. The distribution of actinomycetes in various natural habitats, including soil, ocean, extreme environments, plant, lichens and animals, is described. The collection and pretreatment of test samples from different sources, design principle of selective isolation media, selection of inhibitors, selective isolation procedures of special actinomycetes, and cultivation methods are introduced and discussed.

Part of the book: Actinobacteria

By Yongxia Wang and Yi Jiang

Actinobacterial classification was originally based largely on morphological observation; it is not adequate in itself to differentiate between many genera, because some are so similar morphologically, but differ from their diagnostic chemical composition. In search of reliable classification methods reflecting phylogenetic relationships, at least to the genus level, it has been demonstrated that the analyses of chemotaxonomic markers fulfill these requirements. Chemotaxonomy of actinobacteria is concerned with the distribution of specific chemicals of the cell envelope such as amino acid, sugar, polar lipids, menaquinones, and fatty acid. For some coryneform genera of actinobacteria, analysis of mycolic acid composition is required specially. In this chapter, we will introduce the methods of chemotaxonomy including the extraction, fractionation, purification, and analysis of the target compounds.

Part of the book: Actinobacteria

By Qinyuan Li, Xiu Chen, Yi Jiang and Chenglin Jiang

The traditional phenotypic tests are commonly used in actinobacterial identification. They constitute the basis for the formal description of taxa, from species and subspecies up to genus and family. The classical phenotypic characteristics of actinobacteria comprise morphological, physiological, and biochemical features. The morphology of actinobacteria includes both cellular and colonial characters. The physiological and biochemical features include data on growth at different temperatures, pH values, salt concentrations, or atmospheric conditions, and data on growth in the presence of various substances such as antimicrobial agents, the presence or activity of various enzymes, and with respect to metabolization of compounds. The phenotype is the observable expression of the genotype. Gene expression is directly related to the environmental conditions. Actinobacterial phenotype cannot be based on the simple observation of the organism. Strains of the most closely related taxa should be compared in their phenotypic analysis using identical methods. The comparisons must include the type strain of the type species of the appropriate genera. Furthermore, with the development of technology, microbial physiological and biochemical identification technology is becoming fast, simple, and automated.

Part of the book: Actinobacteria

By Qinyuan Li, Xiu Chen, Yi Jiang and Chenglin Jiang

Actinobacteria is a phylum of gram-positive bacteria with high G+C content. Among gram-positive bacteria, actinobacteria exhibit the richest morphological differentiation, which is based on a filamentous degree of organization like filamentous fungi. The actinobacteria morphological characteristics are basic foundation and information of phylogenetic systematics. Classic actinomycetes have well-developed radial mycelium, which can be divided into substrate mycelium and aerial mycelium according to morphology and function. Some actinobacteria can form complicated structures, such as spore, spore chain, sporangia, and sporangiospore. The structure of hyphae and ultrastructure of spore or sporangia can be observed with microscopy. Actinobacteria have different cultural characteristics in various kinds of culture media, which are important in the classification identification, general with spores, aerial hyphae, with or without color and the soluble pigment, different growth condition on various media as the main characteristics. The morphological differentiation of actinobacteria, especially streptomycetes, is controlled by relevant genes. Both morphogenesis and antibiotic production in the streptomycetes are initiated in response to starvation, and these events are coupled.

Part of the book: Actinobacteria

By Xiu Chen, Yi Jiang, Qinyuan Li, Li Han and Chenglin Jiang

Molecular phylogenetics plays an important role in prokaryote taxonomy and identification. The content of this chapter is to introduce the common application of genetic criteria including 16S rRNA gene sequence nucleotide similarity and phylogeny, DNA G+C content, and DNA–DNA hybridization. However, the genomics era might put forward some new criteria. This chapter emphasizes the methods and basic principles of molecular identification and taxonomy of actinobacteria.

Part of the book: Actinobacteria