Environmental Engineering Reference
In-Depth Information
TAble 6.3
Bacterial Agents That Cause Human Intestinal Diseases
Disseminated by Drinking Water
Microorganism
Disease
Salmonella typhi
Typhoid fever
Salmonella enterica
serotype Paratyphi A
Paratyphoid fever
Salmonella
spp.
Salmonellosis, enteric fever
Shigella
spp.
Bacillary dysentery
Vibrio cholerae
Cholera
Leptospira
spp.
Leptospirosis
Yersinia enterocolitica
Gastroenteritis
Francisella tularensis
Tularemia
Escherichia coli
Gastroenteritis
Pseudomonas aeruginosa
Various infections
Edwardsiella
,
Proteus
,
Serratia
Gastroenteritis
Other factors such as age and general health, as well as previous exposure,
are important. Additional significant influencing factors include the survival
of an organism in water, water temperature, and the presence of colloidal
matter in water.
bacterial Cells: Shapes, Forms, Sizes, and Arrangements
Since the 19th century, scientists have known that all living things, whether
animal or plant, are made up of cells. The fundamental unit of all living
matter, no matter how complex, is the
cell
. A typical cell is a single entity,
isolated from other cells by a membrane or cell wall. The cell membrane
contains protoplasm, the living material found within it, and the nucleus. In
a typical mature plant cell, the cell wall is rigid and is composed of nonliv-
ing material, whereas in the typical animal cell the wall is an elastic living
membrane. Cells exist in a very great variety of sizes and shapes, and their
functions also vary widely. The sizes of cells range from bacteria too small to
be seen with a light microscope to the largest known single cell, the ostrich
egg. Microbial cells also have an extensive size range, some being larger than
human cells (Kordon, 1993).
Bacteria come in three shapes: elongated rods called
bacilli
, rounded or
spherical cells called
cocci
, and spirals (helical and curved) called
spirilla
(rigid cell wall) or
spirochetes
(flexible cell wall). Elongated rod-shaped bacte-
ria may vary considerably in length; they may have square, round, or pointed
ends and may be either motile or nonmotile. The spherical-shaped bacteria
may occur singly, in pairs, in tetrads, in chains, or in irregular masses. The
helical and curved spiral-shaped bacteria exist as slender spirochetes, spiril-
lum, and bent rods (see
Figure 6.1
).
