CHAPTER 1 THE DIVERSE WoRLD OF BACTERIA The single celled organisms called bacteria live on in and around most living and nonliving things With few exceptions bacteria can be seen only with the aid of a microscope and millions of them would fit on the head of a pin PARTS OF A GENERALIZED BACTERIAL CELL OF THE BACILLUS TYPE capsule cell membrane nuclear matter cell wall flagellum Parts of a bacterial cell Encyclopedia Britannica Inc Io
THE DIVERSE WoRLD OF BACTERIA Although some bacteria are harmful many bacterial species are beneficial Bacteria that live in the intestines of humans are essential in digesting food Other species play a role in fermentation a process that produces foods such as yogurt and cheese Bacteria themselves are vulnerable to infection by viruses called bacteriophages The study of bacteria is called bacteri ology It often is integrated with studies of other microorganisms or microbes a diverse group that includes algae archaea fungi and protozoa These combined studies are called microbiology PersICAL CHARACTERISTICs OF BACTERIA Bacteria are prokaryotes that is they have no distinct nucleus sometimes called the command center of a cel and they lack most of the internal structures found in the cells of more complex organisms called eukaryotes Most biologists classify bacteria as constituting one of three domains of living organisms Along with the domain Bacteria these include the Archaea which consists of prokaryotic organisms that have distinct molecular characteristics separating them II
A CLOSER LOOK AT BACTERIA ALGAE AND PROrozo from bacteria and the Eukarya which con sists of all other organisms including plants and animals Scientists divide the bacteria into groups based on shape spherical cells which are labeled as cocci sing coccus rod shaped cells called bacilli bacillus curved rods known as vibrios and spiral shaped bacteria The latter group is further divided into spirilla Bacilli Klebsiella pneumoniae isolated from a lung abscess in a patient with pneumonia A W Rakosy EB Inc I2
THE DIVERSE WoRLD OF BACTERIA spirillum which are rigid thick spirals and spirochetes which are thin and flexible Virtually all bacteria have a cell wall sur rounding a cell membrane Within the cell membrane lies the cytoplasm a jellylike sub stance composedof water proteins and other molecules A single circular strand of DNA a complex molecule that carries all the infor mation about how a living thing will look and B who at a a S Cocci Staphylococcus aureus in a laboratory culture A W Rakosy EB Inc 13
