Ward's World Working with Guides

Page 2 Working with Bacteria and Fungi Bacteria Bacteria are the most numerous and, arguably, the most successful organisms on the planet. They are found virtually everywhere. Their diverse sources of nutrition, rapid rates of reproduction, and adap- tive abilities have enabled them to survive successfully in almost every habitat. From the arctic tundra to the near-boiling hot springs, from the depths of the ocean to the internal organs of other living things, bacteria have thrived since the very earliest beginnings of life on Earth. Bacteria are in the Kingdom Monera. Monerans are prokaryotes — organisms that have a nucleoid and mitochondria. They have DNA chromosomes and are very rarely multi-cellular. Most bacteria are very small, ranging in size from 1 – 10 microns, and their metabolism is highly variable, unlike the "standard" metabolic oxidation modes of higher organisms. There are two major groups in the Kingdom Monera: the Archaebacteria and the Eubacteria. As the name suggests, the Archaebacteria are an "ancient" form that evolved from the bacteria that first existed several billion years ago, when conditions were not conducive to any other type of life. Archae- bacteria are unique in their chemical makeup and the structure of their DNA and include the meth- ane-producers that break down organic matter and produce methane gas. "Salt-loving", or halophilic, bacteria that inhabit the Great Salt Lake and the Dead Sea are another group of Archaebacteria. A third group of Archaebacteria is adapted to thrive in the waters of hot springs at temperatures up to 90°C. This group has also been found in the depths of the oceans in areas around thermal plumes. Eubacteria include both aerobic and anaerobic forms. Two of the major groups are the Cyanobac- teria and the Schizophyta. The Cyanobacteria are the "blue-green algae". They are autotrophic and photosynthetic, but unlike plants, their chlorophyll is in the cytoplasm, not in discreet chloroplasts. Cyanobacteria contain chlorophyll a and a blue pigment, phycocyanin, which together give them their namesake color. They also contain other pigments, and when abundant, they can color the water in which they grow. The Red Sea and the Black Sea owe their names to "blooms" of Cyanobacteria. Schizophyta are the largest groups of heterotrophic Eubacteria. Their classification is based on the Gram test, a staining method developed by a Danish doctor. Crystal violet stain is retained by the cell walls of certain bacteria. The cell walls of other bacteria lose the crystal violet complex by decoloriza- tion and are then counter stained. Bacteria that are stained appear purple under the microscope, and are termed Gram-positive. Those that do not take up the stain appear light pink and are termed Gram-negative. Bacteria are also identified on the basis of their shape. Positive determination must be made by biochemical analysis. The three major bacterial forms are readily identified under the microscope. Spherical bacteria (cocci) may grow close together but do not link. Some species are causative agents of diseases such as strep throat, pneumonia, and gonorrhea. Rod-shaped bacteria (bacilli) includes species that cause anthrax and tetanus, while the spiral-shaped bacteria (spirilli) include species causing cholera and syphilis. However, very few of the large numbers of bacterial species are pathogenic, since the majority are beneficial members of Earth's community, breaking down wastes, recycling nutrients, and enabling higher organisms to digest their food. Introduction

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