Microbial Ultrastructure

Structure and Ultrastructure of Microorganisms: An Introduction to a Comparative Substructural Anatomy of Cellular Organization presents the structure or principle of operation of the electron microscope. This book provides an introduction to the submicroscopical anatomy of the cell in ultrathin sections of tissues or of single-cell organisms. Organized into 30 chapters, this book begins with an overview of the structures discovered by the use of an optical tool for observation. This text then examines the anatomical principle to the nucleus. Other chapters consider the structural organization of chromatin as revealed in electron micrographs of thin sections through cells in different stages of division. This book discusses as well the macronuclei of the ciliates, which plays a significant part in the reproductive mechanism. The final chapter deals with the micromolecular organization of bacterial flagella. This book is a valuable resource for scientists, biologist, physicists, protozoologists, cytologists, biochemists, biophysicists, and research workers.

The modem microbiologist is often a real specialist who has difficulty under standing and applying many of the techniques beyond those in his or her own immediate field. On the other hand, most benefits to modem microbiology are obtained when a broad spectrum of scientific approaches can be focused on a problem. In early studies, electron microscopy was pivotal in understanding bacterial and viral morphology, and we still feel that we will understand a disease better if we have seen an electron micrograph of the causative agent. Today, because there is an increased awareness of the need to understand the rela tionships between microbial structure and function, the electron microscope is still one of the most important tools microbiologists can use for detailed analysis of microorganisms. Often, however, the aforementioned modem microbiologist still thinks of ultrastructure as involving negative staining or ultrathin sectioning in order to get a look at the shape of a "bug. " Many of the newer ultrastructure techniques, such as gold-labeled antibody localization, freeze-fracture, X-ray microanalysis, enzyme localization, and even scanning electron microscopy, are poorly under stood by, and therefore forbidding to, the average microbiologist. Even many cell biologists admit to having difficulty staying in touch with current develop ments in the fast-moving field of electron microscopy techniques.

Mter the discoveryof the tobacco mosaic virus by D. I. Ivanov skU in 1892 [14], the new science of virology was born and began to develop rapidly. The number of viruses now known is enormous and they can infect nearly all animal and plant organisms. Microorganisms themselves are no exception to this rule. Despite intensive study of Vlruses, their origin and nature are still a subject for speculation and hypothesis. The general concept of viruses embraces a wide group of biologically active structures occupying an intermediate position between living and nonliving matter. The dual character of viruses is determined by the fact that, while they do not possess an inde pendent system of metabolism, which is a characteristic feature of every living being, they nevertheless carry within themselves all the necessary information for autoreproduction. A striking feature of the virus is that it consists essentially of two components: a protein envelope and the nucleic acid con tained within it. In contrast to the elementary structural unit of the living or ganism, the cell, which contains two types of nucleic acid (DNA and RNA), the virus particle contains only one type of nucleic acid - either DNA or RNA. It is perhaps this which is responsible for the imperfection of the virus as a living organism.

Plants interact with a large number of microoganisms which have a major impact on their growth either by establishing mutually beneficial symbiotic relationships or by developing as pathogens at the expense of the plant with deleterious effects. These microorganisms differ greatly not only in their nature (viruses, phytoplasmas, bacteria, fungi, nematodes, ... ) but also in the way they contact, penetrate and invade their host. Histology and cytology have brought an essential contribution to our knowledge of these phenomena. They have told us for instance, how specialized structures of the pathogen are often involved in the adhesion and penetration into the plant, how the interface between both organisms is finely arranged at the cellular level, or what structural alterations affect the infected tissues. They have thus set the stage for the investigations of the underlying molecular mechanisms could be undertaken. Such investigations have been remarkably successful in the recent years, expanding considerably our understanding of plant-microorganism interactions in terms of biochemical changes, rapid modifications of enzymatic activities, coordinated gene activation, signal reception and transduction. Biochemistry, molecular biology and cellular physiology have taken precedence in the phytopathologist's set of methods.

Today, the problem of bacteria variability occupies one of the key positions in microbiology. Particular attention is paid to the need to expand research to determine the variability of bacteria under natural habitats. There is still no solid information about the morphological variability of bacteria and its essence. This book is the first to summarise information about the ultrastructure of pathogenic bacteria under different conditions of existence. The results of extensive studies conducted in model microecosystems under various trophic and temperature conditions of cultivation presented here serve to fill this research gap. The book also describes the complex of similar morphological changes that provide the functional usefulness of different species of bacteria in detail, allowing the expression of the assumption that the adaptation mechanisms of heterogeneous populations of microorganisms to changing environmental conditions are universal.

This book offers an in-depth analysis of the cell biology of cyanobacteria, a group of phototrophic microorganisms performing an important function in the biosphere. The chapters present the author’s and her colleagues’ pioneering investigations of the ultrastructure of cyanobacteria under high-light and dark conditions, during irradiation by extremely high fluxes of light, in the course of L-transformation and within model associations and natural symbioses with plants. Diverse patterns of ultrastructural change are illustrated in electron micrographs and schematics. The book further introduces a new concept of “bacterial ultrastructural plasticity” - the reversible rearrangement of ultrastructure in response to environmental changes, as a strategy for finding and investigating cell adaptation mechanisms and intraspecies structural diversity of cyanobacteria and other prokaryotes. It serves as a valuable guide for teaching and research in the field of cell biology of microorganisms and plant-cyanobacteria symbioses.