Microbiology Archive

Shape, Arrangement, and Size

It might be expected that bacterial cells, being small and relatively simple, would be uniform in shape and size. This is not the case, as the microbial world offers considerable variety in terms of morphology. However, the two most common …

Major Fields in Microbiology

Pathogenic microbes, though relatively few in number, have had and continue to have considerable impact on humans. Thus one of the most active and important fields in microbiology is medical microbiology, which deals with diseases of humans and animals. Medical …

Microorganisms and Disease

Although Fracastoro and a few others had suggested that invisible organisms produced disease, most people believed that disease was caused by supernatural forces, poisonous vapors called miasmas, and imbalances among the four humors thought to be present in the body. …

Microscopy and the Discovery of Microorganisms

The earliest microscopic observations of organisms appear to have been made between 1625 and 1630 on bees and weevils by the Italian Francesco Stelluti (1577-1652), using a microscope probably supplied by Galileo (1564-1642). Robert Hooke (1635-1703) is credited with publishing …

Introduction

Microorganisms are defined as those organisms and acellular biological entities too small to be seen clearly by the unaided eye They are generally 1 millimeter or less in diameter. Although small size is an important characteristic of microbes, it alone …

Carbon Cycle

Carbon is the element that defines life, and as such it is everywhere. The exchange of elements between sources and sinks is referred to as flux. Carbon is present in reduced forms, such as┬ámethane (CH4) and organic matter, and in …

Protein Synthesis Inhibitors

Many antibiotics inhibit protein synthesis by binding with the bacterial ribosome and other components of protein synthesis. Because these drugs discriminate between bacterial and eukaryotic ribosomes, their therapeutic index is fairly high but not as high as that of cell …

Cell wall Inhibitor

Penicillins Most penicillins (e.g., penicillin G or benzylpenicillin) are derivatives of 6-aminopenicillanic acid and differ from one another with respect to the side chain attached to the amino group. The most crucial feature of the molecule is the B-lactam ring, …

Characteristics of Antimicrobial Drugs

As Ehrlich so clearly saw, a successful chemotherapeutic agent has selective toxicity: it kills or inhibits the microbial pathogen while damaging the host as little as possible. The degree of selective toxicity may be expressed in terms of (1) the …

Penicillin

Penicillin, the first true antibiotic because it is a natural microbial product, was first discovered in 1896 by a twenty-one-yearold French medical student named Ernest Duchesne. His work was forgotten until Alexander Fleming accidentally rediscovered penicillin in 1928. After returning …