Download presentation
Presentation is loading. Please wait.
1
4-a The Bacteria The Prokaryotic Cell
pps. 77 – 106 The Prokaryotic Cell Size, shape, arrangement of cells Structures external to cell wall
2
(Membrane Transport Quiz)
Animations Bacterial Motility4 (Bacterial Motility Quiz) Membrane Transport4 (Membrane Transport Quiz) Log on to:
3
Prokaryote vs Eukaryote
“Prenucleus” “True nucleus” One circular chromosome Paired chromosomes Not in a membrane In nuclear membrane No histones Histones Organelles (Golgi, ER, cilia, etc.) No organelles Peptidoglycan cell walls Polysaccharide cell walls Binary fission Mitotic spindle
4
Vast heterogeneous group
The Prokaryotic World Vast heterogeneous group Include bacteria, archaea Ubiquitous in nature Very small Unicelluar
5
Differentiated by many factors
Morphology (shape) Chemical composition (~staining) Nutritional requirements Biochemical activities Sources of energy Go through your Lab Manual and list Ex #s next to each of the factors above
6
Morphology, Shapes Coccus (plural = cocci; berries)
Spherical cells Bacillus (plural = bacilli; small staffs) Rod-shaped, often motile Large surface area to volume and adsorption is more effective Coccobacillus Cells not perfectly round (as cocci) Have ‘blunted’ ends, ‘oval’ shape
7
Spirillum (plural = spirilla)
Spiral or curved bodies, one or more ‘twists’ Rigid, fairly inflexible Often motile by external flagella Spirochetes Also ‘spiral’ shaped, but more flexible Motile by an internal flagellum, axial filament Vibrio Comma shaped cells, motile via flagella
8
Average size: 0.2 -1.0 µm 2 - 8 µm Basic shapes
Figures 4.1a, 4.2a, 4.2d, 4.4b, 4.4c
9
Arrangements, Groupings
Arrangement & groupings - useful identification characteristics Cells can remain attached to each other as bacteria divide Cocci tend to display more variation in grouping than rods Cocci divide along more than one axis Rods only divide along their short axis
10
Diplococci = pairs of cocci
Streptococci = chains of cocci Staphylococci = clusters of geometrically arranged cocci (sometimes grape-like) Tetrads = ‘packets’ of 4 cells Sarcinus = ‘packets’ of 8 cells Diplobacilli = pairs of cells Streptobacilli = chains of cells
11
Figures 4.1, 4.2
12
Unusual shapes Most bacteria are monomorphic
Star-shaped Stella Square Haloarcula Most bacteria are monomorphic A few are pleomorphic (Corynebacterium) Figure 4.5
13
Structures External to the Cell Wall
Glycocalyx Flagella Axial filaments Fimbriae, pili
14
Pili Fimbriae Flagellum Glycocalyx Cell wall
15
Glycocalyx The outer surface covered in Functions include:
Polysaccharide, protein, polyalcohols, amino sugars, spp specific Functions include: Attachment Protection from desiccation Protection from ‘attack’ Figure 4.6
16
2 Types of Glycocalyx Capsules Slime layers Capsules are
Closely associated with cells Does not ‘wash’ off easily Slime layer is More diffuse, easily washed off
17
Glycocalyx can be thick or thin, rigid or flexible
Observe with India ink See dark cells with ‘clear outline’ around them Stain does not penetrate glycocalyx Stain? See Ch 3, Fig 3.13a, p 72 & LM
18
Functions Attachment Streptococcus mutans Vibrio cholerae
Produces a slime layer Forms a surface that allows other bacteria to aggregate on tooth surfaces Results in dental plaque Vibrio cholerae Attach to intestinal villi of host Results in cholera
19
Capsules and slime layers are hydrophilic
Avoid Desiccation Capsules and slime layers are hydrophilic Bind ‘extra’ water in the environment Contribute to protection from desiccation Also provide protection from loss of nutrients Holds nutrients within the layer
20
It is difficult to engulf a bacterium that has a capsule
Avoid Phagocytosis It is difficult to engulf a bacterium that has a capsule Streptococcus pneumoniae Able to cause pneumonia and ‘kill’ patient Non-encapsulated cannot cause pneumonia Klebsiella colonize respiratory tract
21
Capsules and Virulence
Bacteria Disease Bacillus anthracis Streptococcus pneumoniae Klebsiella Streptococcus mutans
22
Flagella A tail-like structure Bacterial example:
Projects from the cell body of bacteria Functions in movement Bacterial example: Helicobacter pylori Uses multiple flagella to propel itself Through mucus lining to reach stomach epithelium Figure 4.6 Singular: Flagellum; whip
23
Flagella are Helical Filaments
Rotate like screws Provide several kinds of bacterial motility Consist of protein: flagellin Attach to a protein ‘hook’ Connects to ‘basal body’ rings Gram + microbes have 2 basal body rings Gram negative have 4 rings
24
Gram negative bacterium
Note: 4 rings vs 2 in Gram + Figure 4.8b
25
Flagella and Motility Via rotation of the basal body Rotational ‘speed’ can increase or decrease Moves bacteria through liquid media
26
Flagella Variation Monotrichous (polar) Amphitrichous One flagellum
Vibrio cholera Amphitrichous Have a single flagellum on each end Only one operates at a time Allows bacteria to reverse course rapidly
27
Lophotrichous (one or both ends of cell)
Have multiple flagellum at same ‘spot’ Act in concert to move bacteria in single direction Peritrichous Have a flagella projecting in all directions Escherichia coli
28
Flagella Arrangement
29
Move in one direction called a ‘run’
Flagella: Run, Tumble Move in one direction called a ‘run’ Change in direction called ‘tumbles’ Interruptions in a run, changes direction Caused by reversal of flagella rotation Bacteria with many flagella Proteus Swarms, wavelike movement across media
30
Running and Tumbling View animation: Bacterial Motility4
Figure 4.9 Log on to:
31
Move toward or away from stimuli: TAXIS
Due to chemical stimuli: chemotaxis Or, light: phototaxis If toward the stimuli, called an attractant And the bacteria moves towards it with many ‘runs’ and few ‘tumbles’ If away from the stimuli, called a repellent The frequency of ‘tumbles’ increases as it moves away from the stimulus
33
Flagella and Virulence
The flagellar protein called H antigen is used to identify serovars Among Gram negative bacteria (e.g., E. coli O157:H7) At least 50 different H antigens for E. coli Associated with foodborne epidemics (Ch 1, p. 20)
34
Endoflagella, movement only In spirochetes
Axial Filaments Endoflagella, movement only In spirochetes Anchored at one end of a cell Rotation causes cell to move in spiral motion Fig 4.10
35
Axial Filaments and Virulence
Spirochetes Move through body fluids Treponema pallidum Syphilis Borrelia burgdorferi Lyme disease Fig 26.10 Fig 23.13
36
Fimbriae & Pili Are short, thin appendages
Fimbriae allow attachment to initiate disease Pili join cells to transfer DNA from one cell to another called: Fig 4.11 Conjugation Fig 8.25
37
These structures consist of a protein called pilin
Fimbriae vs Pili These structures consist of a protein called pilin Divided into 2 types, different functions Fimbriae Pili
38
Fimbriae Characteristics
Occur at poles of cells, or all over Number from a few to >hundreds Enable a cell to adhere to surfaces Example: Neisseria gonorrhoreae Causes gonorrhea Fimbriae helps colonize mucus membranes Fig 4.11
39
Usually longer than fimbriae Number only one or 2
Pili Characteristics Usually longer than fimbriae Number only one or 2 Pili join cells to transfer DNA Process called conjugation Fig 8.25
40
Q’s 1. The structure used by bacteria to transfer genetic information is: Flagella Pili Glycocalyx Ribosome Prokaryotic cells Have a single chromosome Lack a nuclear membrane Divide by binary fission Have cell walls containing peptidoglycan All of the above
41
Q’s 1. Which is not a function of glycocalyx
It forms pseudopodia for faster mobility of an organism It can protect a bacterial cell from drying out It can contribute to the disease-causing process It allows a bacterium to stick to a host All of these are involved in bacterial attachment except: Fimbriae Pili Capsules Axial filaments
42
Q’s The cell arrangement shown here is:
Streptococcus Staphylococcus Diplococcus Tetrads Sarcinae The plane in which a bacterium divides determines the arrangement. True False
43
Q’s What is taxis? What are the 3 parts of a flagellum?
Movement towards a stimulus Movement toward or away from a stimulus Movement towards light Movement away from a stimulus What are the 3 parts of a flagellum? Tubulin, flagellin, basal body Flagellin, filament, hook Filament, hook, basal body Tubulin, hook, filament
44
Q’s Which of the following is NOT a structure found in prokaryotic cells? Cilia Axial filaments Peritrichous flagella Flagella Pili
Similar presentations
