5: Bacterial Fine Structures, Functions, and Synthesis Flashcards
3 types of bacterial shapes
- spherical or coccus bacteria (monococcus, diplococcus, staphylococcus, tetracoccus, sarcina, streptococcus)
- rods, or bacillus - bacillus, coccabacillus, palisades, diplobacillus, spore-former, streptobacillus
- curved shapes of bacteria - vibrious, spirilla, spirochaetes
!!! see ppt for pictures
3 types of bacterial cell arrangement
cocci arrangement
bacilli arrangement
others like vibrios, spirilla, and spirochetes
!!! see ppt for pictures
5 types of cocci bacterial arrangement
- diplococci - in pairs
- long chains - repeated divisions in one plane (e.g., streptococci)
- grape-like clusters - division in random planes (e.g., staphylococci)
- tetrads - four cells in square pattern
- cubical packets - eight cells in 3D cube (e.g., Sarcina genus)
!!! see ppt for pictures
type of bacterial arrangement wherein the bacterial cells are Bacilli split only across their short axes
shape of the rod’s end often vary with flat, rounded, cigar-shaped, or bifurcated
bacilli arrangement
4 types of bacilli arrangement
coccobacillus
bacillus
diplobacilli
streptobacilli
palisades
!!! see ppt for pictures
rod-shaped bacteria shaped bacteria that are curved to form distinctive commas or incomplete spirals (arrangement)
vibrios
long rods twisted into spirals or helices that are rigid (arrangement)
spirilla
long rods twisted into spirals or helices that are flexible (arrangement)
spirochetes
2 divisions of bacterial cell components
outer layer or cell envelope - cell wall and plasma membrane
cellular appendages - capsule, fimbriae, and flagella
a general term is a general term for any network of polysaccharide or protein containing material extending outside of the cell
glycocalyx (capsule/slime layer)
capsule - closely associated with cells and does not wash off easily
slime layer - easily washed away zone of more diffuse, unorganized material
7 functions of glycocalyx
- promote attachment to surfaces
- prevent phagocytosis
- protect cell from adverse physical factors
- promote stability of bacterial suspension by preventing aggregation and settling out
- serve as virus receptor
- depot for waste products
- resistance to drying
the layer that lies just outside the plasma (cytoplasmic) membrane composed of mucopeptides (peptidoglycan or murein)
has two parts:
- periplasm (peptidoglycan)
- outer membrane
cell wall
6 functions of the cell wall
- impart shape and rigidity to the cell
- supports the weak cytoplasmic membrane
against the high internal osmotic pressure of the protoplasm (ranges from 5 and 25 atm) - maintains the characteristic shape of the
bacterium - takes part in cell division
- functions in interactions (e g adhesion) with other bacteria and with mammalian cells
- provide specific protein and carbohydrate receptors for the attachment of some bacterial viruses
compare the cell walls of gram-positive bacteria and gram-negative bacteria
gram-positive cell wall: uniformly dense consisting primarily of peptidoglycan (periplasm), with teichoic acid
gram-negative cell wall: very thin peptidoglycan layer and an outer membrane, with lipoprotein, and lipopolysaccharides (LPS)
!!! see module for photos
composition of cell wall peptidoglycan synthesis
overlapping lattice of 2 sugars that are cross linked by amino acid bridges
the two sugars:
- N acetyl glucosamine (NAG, AGA or GlcNAc)
- N acetylmuramic acid (NAM, AMA or MurNAc ): only found in the cell walls of
bacteria (with L-alanine, D-alanine, D-glutamic acid, Diaminopimelic
acid (DPA))
- major barrier in the cell, separating the inside of the cell from the outside
- lipid molecules are arrayed in a double layer with their hydrophilic polar regions externally aligned and in contact with a layer of protein at each surface
- consists of lipoprotein with small amounts of carbohydrate
cell membrane
6 functions of the cell membrane
- controlling the inflow and outflow of metabolites to and from the protoplasm
- housing enzymes
- housing many sensory and chemotaxis proteins that monitor chemical and physical changes
- generates chemical energy i.e., ATP
- cell motility
- mediation of chromosomal segregation during replication
a cellular appendage characterized as a slender threadlike portion, long, hollow, helical filaments originating in the bacterial protoplasm and extruded through the cell wall
flagella
3 parts of a flagellum
filament - longest and most obvious portion which extends from the cell surface to the tip
hook - short, curved segment linking the filament to its basal body
basal body - embedded in the cell membrane, has four rings in gram-negative bacteria (L, P, S, and M)
4 flagella arrangements
- monotrichous - single flagellum
- amphitrichous - single flagellum at both ends
- lophotrichous - tuft of flagella at one or both ends
- peritrichous - flagella surrounding the cell
trichous - hair
lopho - tuft
amphi - both
peri - around
during flagellar synthesis:
- during growth and assembly, protein components are added at the flagellar tip rather than at the base (does not need enzymes)
- both the basal body and the filament have a hollow core
- short, fine, hair like surface appendages
- shorter and thinner than flagella
- originate in the cytoplasmic membrane and are composed of structural protein subunits termed *****
- both in non-motile and motile strains
pili or fimbriae
*****pilins
2 functions of fimbriae/pili
ordinary (common) pili - for adhesions that allow attachment
sex pili - longer and involved in the transfer of DNA during conjugation
an internal bacterial cell component that is a viscous watery solution or soft gel cell material bounded by the plasma membrane
cytoplasm
