Lesson 7: BACTERIAL MORPHOLOGY AND FINE STRUCTURE Flashcards
The major characteristics of bacteria are based on their
size, shape and
arrangements
The size of most bacteria ranges from
0.2 μm (micrometer) to 2.0 μm in diameter and from 2.0 μm to 8.0 μm.
singular: coccus meaning berries
Cocci
usually round but can either be oval, elongated, spherical or elliptical shape. Either they may remain as a single cell or may aggregate together for various configurations
Cocci
represented by single, discrete round cell
Monocuccus
divides but the cells remain attached to each other
Diplococcus
here the cells divide repeatedly in one plane to form chain of cells.
Streptococcus
this consists of four round cells, which divide in two planes at right angles to one another and remain in group of four.
Tetracoccus
the cells divided into three planes forming a structured like bunches of grapes giving and irregular configuration.
Staphylococcus
these cells divide in three planes but they form a cube like configuration consisting of eight or sixteen cells but they have a regular shape.
Sarcina
these are rod shaped or cylindrical bacteria which either remain singly or in pairs.
Bacilli
appear in pairs after cell divides
Diplobacilli
occurs in chain after cell division
Streptobacilli
oval shaped similar to cocci
Coccobacilli
curved, comma shaped bacteria and represented by a single genus
Vibro
spring like with multiple curvature and terminal flagella with fairly rigid bodies
Spirilla
helical and flexible which move by means of axial filaments resembling flagella but contained within an external sheath
Spirochete
Structures external to the cell wall
Glycocalyx
Flagella
Axial Filaments
Fimbriae
Pili
meaning sugar coat
Glycocalyx
are viscous substances that surrounds the cell composed of polysaccharide, polypeptide or both.
Glycocalyx
long outermost part that contains flagellin arranged in helix
filament
Functions of Glycocalyx
- enables bacteria to survive by attaching to surfaces, example: Streptococcus mutans attaches to the surface of the teeth and cause dental carries
- bacterial source of energy when supply is low
- protection to hosts cell by attaching to surface hence preventing the movements of nutrients out of cell during dehydration.
2 forms of glycocalyx
Capsule form and slime layer form
the substance is organized, is firmly attached to
the cell wall, and clinically contributes to the virulence (ability to cause disease) of bacteria due to its capacity to evade phagocytosis by hosts cells
Capsule form
the substance in unorganized and is loosely attached to the cell wall.
Slime layer form
meaning whip
Flagella
Three basic parts of Flagella
Filaments
hook
Basal body
long filamentous appendages that propel bacteria
Flagella
where filament is attached to
hook
anchors the flagellum to the cell wall and plasma membrane. The flagella move by rotating from the basal body either in clockwise or counterclockwise direction.
Basal body
bacterium moves in one
direction
run or swim
movement is termed motility which is can be
presented in different patterns
run or swim
tumbles
swarm
rapid wavelike movement
swarm
periodic abrupt or random interruptions to run or swim
tumbles