: James W. Brown
: Principles of Microbial Diversity
: ASM Press
: 9781683673415
: 1
: CHF 70.90
:
: Medizin
: English
: 100
: DRM
: PC/MAC/eReader/Tablet
: ePUB

Every speck of dust, drop of water, and grain of soil and each part of every plant and animal contain their own worlds of microbes.

Designed as a key text for upper-level undergraduates majoring in microbiology, genetics, or biology,Principles of Microbial Diversity provides a solid curriculum for students to explore the enormous range of biological diversity in the microbial world. Within these richly illustrated pages, author and professor James W. Brown provides a practical guide to microbial diversity from a phylogenetic perspective in which students learn to construct and interpret evolutionary trees from DNA sequences. He then offers a survey of the 'tree of life' that establishes the necessary basic knowledge about the microbial world. Finally, the author draws the student's attention to the universe of microbial diversity with focused studies of the contributions that specific organisms make to the ecosystem.

Principle of Microbial Diversity fills an empty niche in microbiology textbooks by providing an engaging, cutting-edge view of the 'microbial zoo' that exists around us, covering bacteria, archaea, eukaryotes, and viruses.



James (Jim) W. Brown's lasting interest in microbiology was sparked by a single lecture on microbial diversity in an undergraduate microbiology class at Ball State University and by the announcement in that class of the discovery of an entirely new kind of living thing, the 'archaebacteria.' He went on to earn his MS in Microbiology at Miami University and his PhD in the Molecular, Cellular, and Developmental Biology program at The Ohio State University. Jim developed and continues to teach senior-level undergraduate lecture and lab courses in microbial diversity at North Carolina State University (NCSU), which are the genesis of this textbook. He was awarded the NCSU Alumni Association Distinguished Undergraduate Professor award in 2014.

1
What Is Microbial Diversity?


Facets of microbial diversity


What is diversity? Howexactly are organisms either similar to or different from each other? This seems like an easy question in the macroscopic world, but what about microbes?

Morphological diversity


Microbes are often divided by shape into rods, cocci, and spirals. Although these are the most common cell shapes, bacterial and archaeal cells also come in a wide range of other shapes: filaments (branched or unbranched), irregular, pleomorphic (different shapes under different conditions or even in the same culture), star-shaped, stalked, and many, many others.Haloquadratum is a flat, square organism, just like a bathroom tile (Fig. 1.1).

Individual cells of whatever shape can be found in a variety of multicellular arrangements, from simple pairs and tetrads to multicellular filaments, sheets, rosettes, and true multicellular organisms. Many species form highly structured multispecies mats that resemble the tissues of animals and plants that carry out complex biochemical transformations (Fig. 1.2).

Figure 1.1 The tile-shaped halophilic archaeonHaloquadratum walsbyi. (Source: Wikimedia Commons.) doi:10.1128/9781555818517.ch1.f1.1

Figure 1.2 Section of a stratified microbial mat from Guerrero Negro, Baja California. (Copyright 2007, American Society for Microbiology. Photo by John R. Spear and Norman R. Pace.) doi:10.1128/9781555818517.ch1.f1.2

Most bacteria and archaea measure 1 to 5 µm, but they range from 0.1 μm in thickness to over a millimeter. At the low end, it is hard to understand how everything that is needed for life could fit into the cell. At the high end, they can be easily seen without a microscope (Fig. 1.3).

Structural diversity


Many bacteria have “typical” gram-positive (single membrane, thick cell wall) or gram-negative (double membrane, thin cell wall) cell envelopes. However, there is wide variation even within these two major types. Many gram-positive bacteria have an outer membrane, made of mycolic acids rather than glycerol-phosphate esters. Many gram-negative bacteria lack the lipopolysaccharide layer. Many archaea and bacteria (both gram positive and gram negative) have an orderly protein coat, the S-layer (Fig. 1.4). In bacteria, cell walls are composed of peptidoglycan, but there is a surprising range of chemical variations within this type of material. Archaea do not have peptidoglycan cell walls, although some archaeal cell walls contain a related material, pseudomurein.

Figure 1.3 The bacteriumEpulopiscium fishelsoni (ca. 500 μm long) and four cells of the protistParamecium (ca. 100 μm long). (Courtesy of Esther Angert.) doi:10.1128/9781555818517.ch1.f1.3

Microbes have a wide range of external structures: flagella, pili, fibrils, holdfasts, stalks, buds, capsules, sheaths, and so on. They also have a wide variety of internal structures such as spores, daughter cells, thylakoids, mesosomes, and the nucleoid. In reality, microbial cells are just as structurally organized, and diverse, as are eukaryotic cells.

Figure 1.4 A negative-stain electron micrograph of the S-layer ofPyrobaculum aerophilum. Scale bar, 200 nm. (Courtesy of Reinhard Rachel.) doi:10.1128/9781555818517.ch1.f1.4

Metabolic diversity


Macroscopic eukaryotes are not metabolically diverse; they are either chemoheterotrophic (e.g., animals) or photoautotrophic (e.g., plants). Bacteria and archaea have a much