Morphology types: Colonial & Bacterial
Colonial Morphology: -form & structure of bact. colonies
- form from cell division on surface of media
-pigmentation, size, form, elevation, margin, internal struc, & internal consistency of colony
Bacterial Cell Morphology: -form & struct. of cells of bacteria
- size, shape, & arrangement of cells
size, w/ width of 0.5um to 2um & w/ length of 0.5um to 60um
3 basic Cell shapes
Spherical, rod, spiral
-coccobacilli (infrequent) & vibrios (incomplete spiral)
Some bact. species undego binary fission and separate into single cells. Other bact. species remain attached. Arrangements: single, double, quartets, octets, chains clusters
Involution Forms (Abnormal Cellular Morph) of Bacteria
Involution Forms: abnormal cellular forms that appear in old cultures of bacteria
-occur in various odd shapes, such as cells that exhibit swelling and/or rudimentary branching.
-As bacteria age, particularly those in broth cultures in the latter part of the stationary phase or in the death phase, many of the cells exhibit this atypical cell morphology. These involution forms develop, primarily in response to adverse environmental conditions experienced in the media, such as oxygen depletion, nutrient depletion, crowding, excess accumulation of (toxic) bacterial byproducts
In eukaryotic cells, produces an undulating movement and in prokaryotic cells, they produce a motor boat like motion
are long and slender and can be several times the length of the cellwhereas cilia are much shorter
found on a variety of cell-types, such as spirillum bacteria, some bacillus bacteria, and protozoa
enable a microorganism to swim through a liquid environment, whereas cilia enables a fixed cell of a tissue to perform a surface sweeping motion
are comprised of tubulin protein units that are arranged in a "9 + 2" arrangement of eukaryotic microorganisms
Flagella of bacteria, which are prokaryotes, have a relatively simple linear structure of repeating flagellin protein units
Bacterial flagellation: Amphitrichous
one flagellum on one end of the cell and another flagellum on the opposite end of the cell. These are sometimes called polar flagella.
Bacterial Flagellation: Lophotrichous
several flagella iminating from one position on one end of a cell
attached to the plasma membrane and then to the basal body through the use of a hook and ring system
The cell walls are different in Gram(+) bacteria and Gram(-) bacteria, thus the flagellar attachment is different
Gram (+) bacteria
have a cell wall comprised of a single, thick layer of peptidoglycan, located peripheral to the plasma membrane
Gram (+) flagella
comprised of filament, hook and basal body which includes a rod surrounded by an SM ring. The SM ring in the basal body and is attached to the plasma membrane
Gram (-) bacteria
comprised of cell wall membrane that contains lipopolysaccharide (LPS) (LP ring attached here)
cell wall composed of a thin peptidoglycan layer
plasma membrane (SM ring attached here)
Gram (-) flagellum
comprised of a filament, a hook, and a basal body which includes a rod surrounded by an SM ring and an LP ring. The SM ring is attached to the plasma membrane and the LP ring is attached to the cell wall membrane
Nonmotile Bacteria Notes:
Nonmotile bacteria have no mechanism of motility Mayexhibit Brownian movement,which is vibratory movement resulting from the constant bombardment of moving molecules due to random molecular motion of molecules. nonmotile bacterial cells express an irregular "shaking" or "vibratory" motion as they experience a barrage of collisions by the water molecules and other particles of matter of various sizes that are dissolved or suspended in the water. Brownian movement is not true motility. most cocci are non-motile
Motile Bacteria Notes
True motility is translocational movement in some directed path, and is caused by some mechanism of the bacterium itself. Bacteria that are motile include:
1. Virtually all of the true spiral bacteria are motile,
the rigid spirilla have polar flagella
the flexible spirochetes have axial filaments that provides rotatory motion.
2. About half of the bacilli are motile, and their most common mechanism is flagellation. Motility is best observed in young cultures of 18 - 24 hours old because motile bacteria tend to become nonmotile in older cultures in the latter part of the stationary phase and in the death phase.
4 Mechanisms of Motility:
1. Flagellated Motility
2. Gliding Motility
-results from the excretion of slime material from the cell
-results in a gliding motion over a solid surface.
-ex. A variety of blue-green bacteria, some algae-like bacteria, and the protozoa-like slime bacteria have gliding motility
3. Ameboid Motility
-results from cytoplasmic streaming which extends lobes of the plasma membrane, called -pseudopodia, from the cell and pushes the microorganism along.
-ex. the protozoans of the class Sarcodina.
-In spirochete bacteria, rotatory motility results from an axial filament that is located underneath the outermost membrane (cell wall membrane) and is attached to each end (the two poles) of the cell.
-Rotatory motility is a rapid movement characterized by a twisting or wiggling motion that is caused by the flexing of the axial filament. (screw type motion)
-Rotatory motility occurs only in the flexible spiral bacteria, called spirochetes