4-a The Bacteria The Prokaryotic Cell pps. 77 – 106 The Prokaryotic Cell Size, shape, arrangement of cells Structures external to cell wall

(Membrane Transport Quiz) Animations Bacterial Motility4 (Bacterial Motility Quiz) Membrane Transport4 (Membrane Transport Quiz) Log on to: www.microbiologyplace.com

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

Vast heterogeneous group The Prokaryotic World Vast heterogeneous group Include bacteria, archaea Ubiquitous in nature Very small Unicelluar

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

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

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

Average size: 0.2 -1.0 µm  2 - 8 µm Basic shapes Figures 4.1a, 4.2a, 4.2d, 4.4b, 4.4c

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

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

Figures 4.1, 4.2

Unusual shapes Most bacteria are monomorphic Star-shaped Stella Square Haloarcula Most bacteria are monomorphic A few are pleomorphic (Corynebacterium) Figure 4.5

Structures External to the Cell Wall Glycocalyx Flagella Axial filaments Fimbriae, pili

Pili Fimbriae Flagellum Glycocalyx Cell wall

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

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

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

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

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

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

Capsules and Virulence Bacteria Disease Bacillus anthracis Streptococcus pneumoniae Klebsiella Streptococcus mutans

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

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

Gram negative bacterium Note: 4 rings vs 2 in Gram + Figure 4.8b

Flagella and Motility Via rotation of the basal body Rotational ‘speed’ can increase or decrease Moves bacteria through liquid media

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

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

Flagella Arrangement

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

Running and Tumbling View animation: Bacterial Motility4 Figure 4.9 Log on to: www.microbiologyplace.com

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

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)

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

Axial Filaments and Virulence Spirochetes Move through body fluids Treponema pallidum Syphilis Borrelia burgdorferi Lyme disease Fig 26.10 Fig 23.13

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

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

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

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

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

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

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

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

Q’s Which of the following is NOT a structure found in prokaryotic cells? Cilia Axial filaments Peritrichous flagella Flagella Pili