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FCIRMS OF BACTERIA

The word "bacterium'i may have been used for the first tirnein the 185Os when the French investigator Casimir Davaineused the term to mean "rod" or..stalf.,,As the years unfoldedit became apparent that many bacteria are not rodlike, but thenarne remained and soon it was appiied to all microscopicorganisms of that general size and with properties similar tothe rods. In this plate three basic forms of bacteria and theirarrangements are examined and related to their role as diseaseagents.

Color the subheading (a), the four different forms of thebacillus (a1) through (aa) and their titles, and the narnes ofthe related diseases. Use four different shades of the samecolor for these forms.

The rod form of a bacterium is called a bacillus (a; pl.bacilli). Bacilli vary in size, and may be as long as 20 pm oras short as 0.5 pm. Certajn bacllli (Bacillus anthracis) arerectangular with sharply rounded ends (ar); these bacilli causeanthrax (al), a disease of such animals as cows, goats, sheep,and deer- The disease is communicable to humans by air,contaminated meat, and. contact with animals. Certain rod_shaped bacilli are wide at one end and tapered at the other end(club-shaped, a2i e.g., Cornybacterium diphtheriae). They areknown to cause diphtheria (a2). In this disease ofthe respiratorytract, bacterial toxins damage the nerves and the heart. Onetype of bacillu s (Clostridium tetani) isrodlike but swollen atone end (a3). These swollen ends contain endospores, a veryresistant form of the bacterium. Tetanus (ar), a disease causedby these bacteria, is characterized by muscle spasms, seizures,and paralysis ofrespiratory muscles. There are seVeral speciesofbacitli that occur in chains (aa). A streptobacillus is shownhere; str'epto, refers to bacteria linked end_to_end,in chains.Certain streptobacilli cause rat bite fever (aa), a diseasecharacterized by chills, vomiting, and fever.

'Color the subheatling (b), and the five dift"erent forms ofthe coccus and their titles, and the names of the relateddiseases. Use five shades oflhe same color or similar colorswhich contrast with the color used for (a).

The spherical form of a bacterium is known as a coccus(b; pl. cocci). A coccus is about 0.5 pm in diameter. Somecocci called dipiococci are paired (diplo-, double). One speciesof diplococcus (streptococcus pneumoniaie) has tapered sides(b') and causes pneumonia (b'), an inflammation of the airspaces of the lungs accompanied by fluid formation. Another

type of diplococcus (Neisseia gonorrhoeae) (b2) resemblestwo tiny beans lying face to face. ,iy'. gonorrhoeae causesgonorrhea (b2), a disease transmifted by sexuai contact. Thestreptococcus is a well-known group of cocci characterizedby individuals in a chain (b3). ..Strep rhroat', (b3), a seriousinfection of the pharynx, is c.aused by a species of strepto_coccus. In contrast, a harmless species of streptoccccus is oneof the "active cultures" in a cup of yogurt. Acubelike packetoffour or eight cocci (ba)is called a sarcina. One sarcina calledMicrococcus luteus is a common nonpathogenic inhabitant ofthe human skin (ba). Another type of coccus, calledstaphylococcus, ociurs in clusters (b5) ind produces toxins infood resulting in staphylococcal food poiioning (bs). Otherstaphylococci enter hair follicles and inflame theikin causingboils or "staph infection" (not shown).

Color the subheading (c), the three different forms of thespiral and their titles, and the names of the rela&ed diseases.Use three shades of the same color which contrasts withthe colors used for (a) and (b).

A third tbrm of a bacterium is the spiral (c). These bacteriaare about 15 gm in length. In the spiral form called the vibrio(cr), the bacterium has only a single turn. appearing curved,like a comrna. One vibrio causes cholera (c'), i sdrious Oisordercharacterized by vomiting, diarrhea, and cramps. Severedehydration caused by Vbrio cholerae is induced by toxinsthat interfere with sodiurn absorption in the intestines. Anotherform of spiral bacteria is the spiriiium (pl. spirilla). Thespirillum resembles a corkscrew, with the spiral making severaltums (c2). ltre spirillum possesses a rigid cell wall with flagellafor movement. This bacterium causes rat bite fever (cr), whiphis similar in.symptoms to the rat bite fever caused bystreptobacilli. A spirochete is a spiral bacterium that has thecorkscrew form but a flexible cell wall and no flagelia (ci). Ituses axial filaments to move in a snakelike manner. Aspirochete (Treponema palli,ium) is responsible for syphilis(c3), a disease in which the bacteria enter the tissues throughbreaks in the skin, such as the skin of the genital organs.

The anatomicai pattem of a bacterium can be of greatpractical vaiue. In the diagnostic laboratory for example; atechnician may note the characteristic diplococci ofgonorrheain a patient's urine sample and report thjs observation to thephysician. The diagnosis of syphitis is aideC considerably bylocating tlte characteristic spirochetes in materiai from a skinlesion. And strep throat may be pinpointed by.observingstreptococci in bacterial colonies isolated from the throat.

FORMS OF BACTERTA

tsAG0LLUS t,r

ANTHRAX,.

A. EOPHTHEROA ,,

GLUB ,,

NON-PATH@GtrN0G u'

bo

TETANUS ^,

F@OE POOS@NONG b5

b5

Staphylococcus

llFORMS OF BACTERIA

RAT tsOTE FBVER

Stre ptobacil I us

GHAON ^.

STREP THROAT

Slre pto cocc us

G@GGUS tui

PNEUnfl@N0A u' GON]@RRHEA

{**

o(

%$

oqy

@i6P,sSarci na GLUSTER u'

I

_lFAGKET r*

SF0RAL r.r

GHOTERA .,

Vibrio

RAT BOTE FB4ER .' SVtrHOLOS .,

Spirillumc3

-- Spirochete

SON]GtESPORAT .. FLAGELLUM ., N@ FLAGEL0-UIM .'