UNIT 1/L5/ BACTERIA FLAGELLA

Counterclockwise rotation of the flagella causes propels the bacterium in long, straight or curved runs without a change in direction towards an attractant or away from a repellent; clockwise rotation induces a tumbling motion with frequent changes in direction. This best describes what?

. Chemotaxis in bacteria with peritrichous flagella

Counterclockwise rotation of flagella pushes the bacterium forward towards an attractant or away from a repellent; clockwise rotation pulls the bacterium backward. This best describes what?

Chemotaxis in most bacteria with polar flagella

inflammation

a process in which blood vessels dilate and become more permable, thus enabling the body defense cells and defense chemicals to leave the blood and enter the tissues. Acute inflammation is usually localized, protective response to tissue injury. Excessive or chronic inflammation, however, may lead to tissue destruction.

Chemotaxis-

a response to a chemical gradient of attraction or repellent molecules in a bacterium's environment

FILAMENT

a rigid, helical structure that extends from the cell surface. It is composed of the protein flagellin arranged in helical chains so as to form a hollow core

amphitrichous

a single flagellum at both ends of the organism

monotrichous

a single flagellum, usually at one pole

antigen

a substance that reacts with antibody molecules and antigens receptors on lymphocytes. An immunogen is an antigen that is recognized by the body as nonself and stimulates an adoptive immune response.

. Compare and contrast how bacteria with peritrichous flagella and bacteria with polar flagella carry out taxis

If a bacterium has a peritrichous arrangement of flagella, such as Escherichia coli, Salmonella, Proteus, and Enterobacter, counterclockwise rotation of the flagella causes them to form a single bundle that propels the bacterium in long,straight or curved runs without a change in direction. Clockwise rotation causes the flagella to be pushed apart form one another causing a tumbling motion. Everytime the bacterium tumbles it reorients itself in a new direction. Most bacteria with polar flagella. Such as Pseudomonas aeruginosa, can rotate their flagella both clockwise and counterclockwise, it pushes the bacterium forward. When it rotates clockwise, it pulls the bacterium backward. These bacteria change direction by changing the rotation of the flagella. Everytime the bacterium stops, it reorients itself in a new direction.

PAMPs -( Pathogen-associated molecular pattern)

Molecules unique to microorganisms that are not associated with human cells. The include LPS, peptidoglycan, lipotiechic acids, mannose, flagellin, pilin, bacterial DNA, and viral double-stranded RNA.

Many bacteria that infect the urinary tract and the intestinal tract are motile. Why might this be an advantage?

Motility and chemotaxis enables bacteria to swim through mucus and make contact with the mucosal epithelium.

What enable certain spirochetes to penetrate tissues as well as enter the lymphatics and bloodstream enabling their dissemination to other body sites?

Motility, chemotaxis, and invasins

What is the significance of flagellin to innate immunity?

a PAMP that binds to PRRs on defense cells

BASAL BODY

consists of a rod and a series of rings that anchor the flagellum to the cell wall and the cytoplasmic membrane

PRRs-( Pattern-recognition receptors)

molecules on or in with host cells that are able to recognize or bind to pathogen-associated molecular patterns in order to induce innate immunity.

flagella

organelles of locomotion for most of the bacteria that are capable of mobility.

antibody

specific protein configuration produced by B-lymphocytes and plasma cells in response to an antigen to react with an antigen during humoral immunity. There are five classes of human antibodies IgG, IgA, IgM, IgD, and IgE. Also known as immunoglobulins (Ig).

epitopes

the actual portions or fragments of an antigen that reacts with receptors on B-lymphocytes and T-lymphocytes, as well as with free antibody molecules. Usually equivalent to 5-15 amino acids or 3-4 sugar molecules.

lophotrichous

two or more flagella at one or both poles.

B-lymphocytes

white blood cells that play a large role in humoral immunity. Their principal functions is to make antibodies against antigens. They recognize antigens by B-cell receptors (BCR).

taxis

A motile response to an environmental stimulus. Bacteria can respond to chemicals (chemotaxis), light (phototaxis), osmotic pressure (osmotaxis), oxygen (aerotaxis), and temperature (thermotaxis).

Briefly describe how bacterial flagella and chemotaxis may play a role in the Pathogenicity of some bacteria

Motility and chemotaxis probably help some intestinal pathogens to move through the mucous layer so they can attach to the epithelial cells of the mucous membranes. In fact, many bacteria that can colonize the mucous membranes of the bladder and the intestines are motile. Motility probably helps these bacteria move through the mucus in places where it is less viscous. Motility and chemotaxis also enables spirochetes to move through viscous environments and penetrate cell membranes. Motility and invasins may also enable the spirochetes to penetrate deeper in tissue and enter the lymphatics and bloodstream and disseminate to other body sites.

State what provides the energy for bacterial flagellar rotation

The MOT proteins surround the MS and C rings of the motor and function to generate torque for rotation of the flagellum. Energy for rotation comes from the proton motive force (def) provided by protons moving through the MOT proteins.

opsonization

The attachment of microbes and other foreign cells of phagocytes by antibody molecules such as IgG and complement proteins such as C3b. Also called enhanced attachment or immune adherence.

Humoral Immunity

The production of antibody molecules in response to an antigen mediated by B-lymphocytes.

State how bacterial flagella may play a role in the initiation of innate immune defenses.

The protein flagellin in bacterial flagella is a PAMP that binds to pattern-recognition receptors or PRRs on a variety of defense cells of the body and triggers innate immune defenses such as inflammation, fever, and phagocytosis

repellent

a chemical a bacterium wants to move away from.

attractant

a chemical a bacterium wants to move towards.

HOOK

a flexible coupling between the filament and the basal body.

cytokines

a wide variety of intracellular regulatory proteins produced by many different cells in the body which ultimately control every aspect of the body defense. They activate and deactivate phagocytes and immune defense cells, increase or decrease the functions of the different immune defense cells, and promote or inhibit a variety of nonspecific body defenses.

macrophages

are derived from monocytes and are located throughout the body. Macrophages are important phagocytes, producing inflammatory cytokines, and can capture and present protein antigens to effector T-lymphocytes.

NK cells - ( natural killer cells)

are lymphocytes that lack B-cell receptors and T-cell receptors. They kill cells bound by antibody or lacking MCH-I molecules on their surface.

T-lymphocytes

are white blood cells that play a large role in humoral immunity, cell-mediated immunity, and innate immunity. They circulate back and forth between the blood and the lymphoid system of the body. They recognize antigens by way of their T-cell receptors (TCR).

Leptospira

causes Leptospirosis. Transmitted by the blood and urine of affected rodents, Leptospira usually enters by cuts and contact with mucuous membranes. It may eventually enter the lymphatics and blood and be carried to the liver

Borrelia burgdorferi

causes Lyme disease. Transmitted by infected deer ticks, the spirochete may spread from the initial bite, be picked up by the lymphatic and blood, and be carried to many other sites in the body.

Treponema pallidum

causes syphillius. Transmitted sexually,the spirochete usually enters via cuts or abrasions on the skin of the genitalia or contact with mucuous membrane. It may eventually enter the lymphatic and blood and be carried to many other areas of the body

cytotoxic T-lymphocytes

defense cells derived from T8-lymphocytes that recognize and destroy infected cells and tumor cells. By way of TCR/CD8 molecules on their surface, the CTLs bind epitopes from endogenous antigens bounds to MHC-I molecules on the surface of infected cells or tumor cells and kill that cell by inducing apoptosis.

proton motive force

energy gradient resulting in hydrogen ions (protons) moving across a membrane from greater to lesser hydrogen ion concentrate.

peritrichous

flagella over the entire surface.

axial filaments

internal flagella found only in the spirochetes

Chemoreceptors

regulated by chemotaxis located in the cytoplasmic membrane or periplasm of the bacterium bind chemical attractants or repellents

rotor

rotating part of the rotary system such as the motor.

What are the 3 basic parts of bacterial flagellum ?

the filament, hook, and basal body

Cell-mediated Immunity

the production of cytotoxic T-lymphocytes and cytokines in response to an antigen mediated by T-lymphocytes.

stator

the stationary part of the rotary system such as the motor.