secondarymetabolism

Secondary metabolism refers to metabolic pathways that produce secondary metabolites—organic compounds that are not essential for basic cellular functions such as growth, development, or reproduction. In contrast to primary metabolism, which provides essential biomolecules and energy, secondary metabolism yields compounds whose ecological roles vary with environment and organism. These metabolites are often produced in specific tissues or developmental stages and can be constitutive or inducible.

The chemical diversity of secondary metabolites is vast, including alkaloids, terpenoids, polyketides, nonribosomal peptides, phenolics, and more. They arise from specialized biosynthetic pathways that often diverge from primary metabolism and may involve gene clusters in microorganisms or complex, multi-gene networks in plants. In microbes and fungi, biosynthetic genes for a given metabolite are frequently organized in clusters, enabling coordinated regulation and facilitating genome mining for novel compounds.

Ecological functions of secondary metabolites are diverse. They play roles in defense against herbivores and pathogens, allelopathy, wound and environmental stress responses, pollinator and seed-disperser interactions, and communication or competition with other organisms. Their production is often inducible by stress, nutrient status, or developmental cues, and it can be tissue- or life-stage specific.

Applications and research of secondary metabolism are wide-ranging. Many metabolites have pharmaceutical value, including antibiotics, anticancer agents, immunosuppressants, and analgesics, while others are used as agrochemicals, fragrances, or dyes. Modern efforts combine genomics, metabolomics, and synthetic biology to discover new compounds, elucidate biosynthetic pathways, and engineer production in native or heterologous hosts.