Comparative aspects of development and differentiation in actinomycetes.

Abstract

INTRODUCTION ............................................................. 469 Aims and Scope .............................................................. 469 Suitability of Various Types of Cultures for Studies of Development and Differentiation .................................................................. 470 Growth of Actinomycetes ................. ................................... 471 LIFE CYCLES IN THE ACTINOMYCETALES ....... ......................... 472 Generalized Scheme of Events Accompanying Reproduction ...... ............. 472 Multiplicity of Reproductive Patterns ......... ............................... 474 Rare and Unconfirmed Modes of Reproduction ........ ........................ 475 STATIC ASPECTS OF DIFFERENTIATION ........ .......................... 475 Differentiation within Colonies ............ .................................. 475 Differentiation of the Mycelium: Primary versus Secondary Mycelium ..... .... 476 Cellular Differentiation ................. .................................... 477 Amycelial Structures ....................................................... 479 Modes of Spore Formation ................ ................................... 481 Spores .................................................................. 483 Structure ................................................................. 483 Composition .............................................................. 484 Physiology ............................................................... 486 DYNAMIC ASPECTS OF DIFFERENTIATION ....... ......................... 487 Age-dependent Changes in Actinomycete Cells ....... ......................... 487 Environmental Conditions and Morphogenesis ....... ......................... 488 Metabolic Activity and Morphogenesis ......... ............................... 489 Environmental Factors in Control of Sporulation ....... ...................... 489 Nutritional limitations and sporulation: desiccation and other triggers ....... 489 Nutritional requirements for sporulation ........ ........................... 490 Supression of sporulation .............. .................................... 491 Sporulation under natural conditions ......... .............................. 491 Internal Factors in Control of Sporulation ...... . ............................. 491 Variants and mutants with impaired differentiation ...... ................... 492 Sporulation and chromosomal genes ......... .............................. 493 Sporulation and plasmids ............. ..................................... 493 Proteolytic activity and sporulation and the question of RNA polymerase modification .................................................................. 493 Involvement of specific factors in regulation of sporulation ..... ............. 494 Spore Germination and Types of Dormancy Encountered ...... ................ 495 Constitutive dormancy of thermoresistant endospores and an overall picture of germination ........................................................... 496 Possibility of an alternative way for release from dormancy ..... ............ 496 Germination of exospores .............. .................................... 498 DIFFERENTIATION AND SECONDARY METABOLISM ...... ................ 500 Points of Similarity in Origin and Flow ......... ............................. 500 Prospects for Involvement of Antibiotics and Pigments in Regulation of Metabolism..................................................................... 503 Antibiotics and Their Components as Possible Building Blocks ..... ........... 504 LITERATURE CITED ........................................................ 506