General Microbiology Ch4

Dr. Pipkins General Micro WCU

What makes an organism living? (7)

Growth/Development

Reproduction

Respond to Stimuli

Transport Nutrients

Metabolism/Enzymes

Heredity/DNA

Cellular Organization

What are the prokaryotic structures?

Cell Membrane

Ribosomes

Cytoplasmic Matrix

Nucleoid/Chromosomes

Glycocalyx

coating of macromolecules that protects cell, mostly by retaining moisture; consists mainly of polysaccharides and proteins

What are the 2 parts of the glycocalyx?

Slime Layer and Capsule

Slime Layer of Glycocalyx

Uneven, nonuniform distribution

Loosely associated with cell

Outermost Layer

Capsule of Glycocalyx

Even, uniform distribution

Tightly associated with cell

Helps pathogenic bacteria go through cell membrane

If both capsule and slime layer are present; capsule is deeper and slime layer is superficial

Biofilm

Cooperative complexes in which microbes communicate via chemical signals

Where do biofilms form?

Moist, solid surfaces

Soft tissue in living organisms

Water-air interfaces

What do biofilms do?

Provide protection from host responses and antibiotics

Is the glycocalyx present on all prokaryotes?

No

What structure plays an important part in the formation of biofilm?

Glycocalyx

Planktonic Bacteria

Bacteria that are free-living and unassociated with a biofilm

Quorum Sensing

Using chemical signals to determine population density (bacteria communicate with one another to form a biofilm)

Cell Envelope

Cell Wall and Cell Membrane

Cell Membrane

Semipermeable membrane surrounding the cytoplasm of a cell

Made of a selectively permeable Phospholipid Bilayer

Cell Wall

Determines cell shape

In bacteria, consists mainly of peptidoglycan

Peptidoglycan

Network of long polysaccharide chains (glycans) cross-linked by short peptide fragments

Often target of antibiotics

Consists of 2 alternating glycans in long strands (NAG & NAM)

(In bacteria, not archaea)

What are the 2 different groups of bacteria (when considering peptidoglycan)?

Gram +: Not much space between membrane and wall

Gram-: Space between wall and inner membrane. Contains additional outer membrane, more selective

SLIDE 22

Teichoic and Lipoteichoic Acids

Only in Gram +

Involved in cell wall maintenance, cellular expansion during cell division, and binding to tissues

Gram Positive

Thick cell wall with a dense peptidoglycan layer

Located directly over the plasma membrane

Gram negative bacteria

Thin peptidoglycan layer covered by an additional lipid membrane

Separated from the plasma membrane by a periplasmic space

Periplasmic Space

Space in gram negative bacteria between peptidoglycan and plasma membrane

What unique structures are found in a gram negative cell wall?

Porins

Lipopolysaccharides (LPS)

Outer Membrane

Porins

Unique transport proteins, found in outer membrane

Lipopolysaccharides (LPS)

Forms outer membrane

*Becomes toxic when released in a host during cell lysis (Breaking down of cell membrane)

Outer Membrane

Makes cell less permeable to antibiotics and chemicals, making them harder to kill

Gram Stain

Differential test that distinguishes between gram-positive and gram-negative cell walls

SEE SLIDE 27 FOR STEPS****

What color are gram positive bacteria after performing a gram stain? Negative?

Positive are dark purple and negative are a pink/red

What bacteria have an atypical cell wall?

Mycobacterium tuberculosis

Mycoplasmas

Mycobacterium tuberculosis

gram positive-like cell wall structure with addition of fatty acid chains called mycolic acid

What are mycolic acid bacteria distinguished by?

Acid fast stain (Cells hold pink stain in presence of acid - all others stain blue)

Mycoplasmas

Bacteria that completely lack a cell wall

Pleomorphic

Found in multiple shaped in nature

How to mycoplasmas prevent bursting without a cell wall?

They have waxy lipids like cholesterol in the cell membrane that prevent the cell from bursting.

Archaea Cell Wall

No peptidoglycan

Pseudomurein- similar to peptidoglycan

S Layer- protein or glycoprotein lattice surrounding the cell

External Prokaryotic Appendages

Fimbriae

Pili

Flagellum

Fimbriae

Short, hair-like appendages that aid in adhesion to surfaces or other cells

Flagellum

Long, whip-like appendage used to propel an organism through a fluid envirionment

Pili

Stiff, filamentous appendages that function in DNA exchange (Conjunction)

Conjunction

Transfer of genetic material between bacterial cells by direct cell-to-cell contact

Monotrichous Flagellar Arrangement

Single flagellum at one endL

Lophotrichous Flagellar Arrangement

Tuft of flagella emerging from one end

Amphitrichous Flagellar Arrangement

Flagella at both ends of the cell (single or multiple)

Pertrichous Flagellar Arrangement

Flagella dispersed randomly over the cell’s surface

Runs

Smooth, linear motion caused by a counterclockwise rotation

Tumbles

Breaks in movement in order to change direction; caused by clockwise rotation

Chemotaxis/Phototaxis

Movement of a motile cell in response to a chemical or light stimulus. Movement towards or away from the substance follows the increasing or decreasing concentration gradient

Periplasmic Flagella

Internal flagella enclosed between an outer sheath and the cell wall peptidoglycan

Where is periplasmic flagella found?

Corkscrew-shaped bacteria known as spriochetes

What do periplasmic flagella do?

Produce cellular motility by contracting and twisting/flexing

Cytoplasm

Dense, gelatinous solution of sugars, amino acids, and salts enclosed by the cell membrane

Nucleoid

Undifferentiated space in the cytoplasm that contains the genetic material of the bacterium

What are the two parts of a nucleoid?

Chromosome and Plasmids

Chromosome

Large, circular DNA strand that contains all the normal genetic information of the cell

Plasmids

Small, circular DNA; separate from the chromosome

*Not essential to bacterial growth and metabolism

*Easily transferred from cell to cell

*Often encode genes that increase pathogenicity

Ribosomes

Sites of protein synthesis dispersed throughout the cytoplasm

Actin Cytoskeleton

Internal network of protein fibers that help shape the cell

Inclusion Bodies

Cytoplasmic aggregates that vary in size, number, and contents

What size is a prokaryotic ribosome?

70S

Types of Inclusion Bodies

Protein shells containing enzymes and reactants used in metabolic processes

Vesicles containing lipids or carbohydrates that can be accessed when nutrients are scarce

Gas Vesicles

Thylakoids

Magnetosomes

Gas Vesicles

Found in some aquatic bacteria, provide buoyancy

Thylakoids

Chlorophyll-containing structures found in photosynthetic cyanobacteria

Magnetosomes

Iron oxide deposits used to orient the bacteria with the earth’s magnetic field

Endospores

Specialized survival structure produced by select gram positive bacteria

What two phases of the life cycle does an endospore swap between?

Vegetative Cell- Metabolically active and growing

Endospore- Dormant, tough, and non-reproductive structure capable of high resistance and very long-term survival

Sporulation

Process of developing into an endospore

Germination

Process of returning to a vegetative cell

Binary Fission

Method of asexual reproduction in which most bacteria reproduce

Steps of Binary Fission

1. Chromosome replication and cell enlargement

2. Chromosome division and septation

3. Completion of cell compartments

4. End of cell division cycle