Procaryotic Profiles: The Bacteria and Achaea Cell Structure

Created by Kandisjns 

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Morphology

science / study of form & structure

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)

Note:

Some bact. species undego binary fission and separate into single cells. Other bact. species remain attached. Arrangements: single, double, quartets, octets, chains clusters

cocci

spherical (ball shaped) cell

diplococci

pairs of spherical cells

tetrad

squared form of 4 spherical cells

Sarcina

cuboidal form of 8 spherical cells

streptococci

chains of spherical cells
ex. streptococcus

Staphylococci

clusters of spherical cells
ex. staphylococcus

Bacilli Bacteria

cylindrical (rod shaped) cells

Bacilli

single, separated rod shaped cells

diplobacilli

pairs of rod shaped cells connected end to end

streptobacilli

chains of rod shaped cells connected side by side

coccobacilli

short, thick rod shaped cells w/ dome ends

Spiral bacteria

helical cells

spirilla

rigid spirals

spirochetes

flexible spirals

vibrio

incomplete spirals & include "comma", bent rod, slow S shapes cells

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

Flagella

undulations of thread like-structures, called flagella(or may be due to cilia).

Flagella

In eukaryotic cells, produces an undulating movement and in prokaryotic cells, they produce a motor boat like motion

Flagella

are long and slender and can be several times the length of the cellwhereas cilia are much shorter

Flagella

found on a variety of cell-types, such as spirillum bacteria, some bacillus bacteria, and protozoa

Flagella

enable a microorganism to swim through a liquid environment, whereas cilia enables a fixed cell of a tissue to perform a surface sweeping motion

Flagella

initiated, and indeed are outgrowths of the plasma membrane of a cell

Flagella

are comprised of tubulin protein units that are arranged in a "9 + 2" arrangement of eukaryotic microorganisms

Flagella

Flagella of bacteria, which are prokaryotes, have a relatively simple linear structure of repeating flagellin protein units

Type of Bacterial flagellation: Monotrochous

one flagellum on one end of the cell.

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

Bacterial Flagellation: Peritrichous

many flagella around the entire surface of the cell.

Flagellum

attached to the plasma membrane and then to the basal body through the use of a hook and ring system

Flagella

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)
cytoplasm

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

Bacterial Motility

Bacteria can be divided into two groups: nonmotile or motile.

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.
4.Rotary Motility
-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

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