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Axial filaments

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Seen in spirochetes. These are like
flagellum but are enclosed within a sheath surrounding the cell.

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Gram-positive cell walls consist of

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many layers of
peptidoglycan and contain lipoteichoic acids.

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Gram-negative bacteria have a

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lipoprotein-
Lipopolysaccharide-phospholipid outer membrane surrounding a thin peptidoglycan layer

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Outer membrane protects gram- negative cells from

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phagocytosis, penicillin, lysozymes, and other chemicals

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Non-selective media

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one that contains general nutrients needed to
sustain a wide variety of microorganisms. These can be in fluid form (often called broth), or solid form which is broth containing agar. The latter is like “Jello”.

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Differential media

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in addition to general nutrients, it contains other
ingredients which produce visual differentiation between microorganisms. An example is blood in the medium that allows various types of streptococci to leave different signs on the agar surface, eg. green discoloration around colonies indicates alpha-hemolytic streptococci, a clear zone signifies beta-hemolysis, and no effect denotes gamma-hemolysis.

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Selective media

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These contain ingredients such as dyes or antibiotics
which prevent growth of certain microorganisms while permitting others to grow. An example is Sabouraud dextrose agar which is selective for fungi.

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Most bacteria reproduce via

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binary fission (i.e., two new cells are
produced by one parent cell). Duplicates of the cell constituents form at either end of a single cell which then separates into 2 cells by in-growth of the cell membrane and wall.

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Growth curve

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. 1) Lag phase—period of intense metabolic activity but no increase in cell number. 2) Log phase or exponential growth phase—cell number increases in an exponential manner; generation time is the average time for the cell to divide. 3) Stationary phase-total number of viable cells is constant; metabolic activity slows. 4) Phase of decline or death phase - number of viable cells decreases.

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Measurement of growth

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Population counts—cell numbers cab be measured by viable plate
counts (number of colonies on an agar medium). Counts are expressed as colony-forming units (CFU) for bacteria or plaque-forming units (PFU) for viruses. (Viruses are inoculated on an agar medium containing a dense lawn of live cells or bacteria on the surface. Where viruses land they lyse these cells forming a clear plaque which can be seen and counted as the number of viral particles present.)
b. Cell mass can be measured by turbidity of culture in a liquid medium.

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Anabolism

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Biosynthetic reactions that use energy in which
macromolecules such as nucleic acids, proteins, lipids, and polysaccharides are synthesized.

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Catabolism

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degradative reactions that release energy when
complex compounds are broken down into smaller units .

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Transcription

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synthesis of messenger RNA (mRNA) from
DNA template.

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Translation

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synthesis of protein in the ribosomes from an
mRNA template.

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Conjugation

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a. Transfer of genetic material between two living bacteria that are in
physical contact.
b. Plasmids are most frequently transferred

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Transduction

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a bacterial virus (bacteriophage) transfers genetic
material to another bacterium

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Transformation

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the direct uptake of donor DNA by a recipient cell

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Transposons

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jumping genes” small segments of DNA that can move
from one region of a chromosome to another region of the genome.

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Classification of infections

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a. Systemic—can affect a number of tissues and organs
b. Subcutaneous—beneath the skin
c. Cutaneous (superficial, Tinea infections
d. Opportunistic—generally harmless, but can become pathogenic in
a debilitated host.

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inflammatory reaction

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? PMNs and macrophages engulf and destroy foreign particles or cells, mast cells and basophils release histamine at the damaged tissue which cause acute inflammation, Histamines cause capillaries to leak, releasing phagocytes, platelets move out of capillary to seal the wounded area

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lgG

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secondary immune response. Its the only immunoglobulin capable of crossing placenta barriers.

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lgM

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primary immune response.

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lgA

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tears, saliva. bile, urine, and colostrum

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lgE

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immediate hypersensitivity reactions. It binds to mast cells where it activates them to release histamine

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Type l

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. Anaphylactic (" immediate") hypersensitivity: lgE mast and basophil cells release large amounts of histamine Examples asthma attacks, hay fever, hives, anaphylactic shock

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Type ll.

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Cytolytic hypersensitivity. example is a mother’s immune system destroying her baby’s red blood cells

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Type lll. lmmune complex hypersensitivity:

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Too many antigen-antibody immune complexes are deposited in tissues. Examples are serum sickness and arthus reactions

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Type lV. Delayed hypersensitivity:

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T lymphocytes. Examples are contact dermatitis, poison ivy, graft rejection, tuberculin skin reaction

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Antibody (Ab)

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a protein that is produced as a result of the introduction of a foreign antigen and has the ability to combine with the antigen that stimulated its production.

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Antigen( Ag)

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a non-self substance that can induce a detectable immune response when introduced into a living host.

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B-cell ( also B –lymphocyte)

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B –cells are the precursors of plasma cells that produce antibody.

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Chemotaxis

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a process whereby phagocytic cells are attracted to the vicinity of invading pathogens.

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Complement

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A complex group of serum proteins which makes holes in the membranes of bacteria or sometimes host cells killing them. It works only if an antibody is attached to the foreign body or cell.

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Cytokines

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are small proteins secreted by host defense cells (mainly lymphocytes) that act as signaling agents to other cells. In Immunity, cytokines activate other cells to destroy or inhibit a foreign agent or cell in the body or stimulate elements of the immune systems.

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Cytolysis

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the lysis of bacteria or of cells such,as tumor or red blood cells by the membrane attack complex derived from activated complement or immune cells.

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Histocompatible

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having the same antigens as the self-antigens

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lmmune response

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development of resistance (immunity) to a foreign substance ( e.g. infectious agent); it can be antibody mediated (humoral) cell mediated (cellular), or both.

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lmmunoglobulin

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a glycoprotein molecule that may function as an antibody. All antibodies are immunoglobulins, but not all immunoglobulins have antibody function.

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lmmunodeficiency

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Inability of the immune system to perform normally and often results in increased susceptibility to infection. Example: Drug – induced immunosuppression

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Interferon

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low molecular-weight proteins elaborated by viral-infected host cells that protect non-infected cells from viral infection.

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Lymphocyte

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a “white blood cell” that includes the T-cells and B-cells which have primary roles in immunity.

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Macrophage

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a phagocytic cell derived from the mononuclear cell or monocyte (a white blood cell) found in the blood. In inflammation the monocytes exit from blood vessles and become macrophages in the tissue. Macrophages also have roles in humoral and cellular immunity.

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Major histocompatibility complex (MHC)

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a cluster of genes located in close proximity that determines histocompatibility antigens for members of a species. These antigens become the “self” labels.

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Monocyte

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a circulating phagocytic blood cell that develops into tissue macrophages

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Opsonin

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a substance capable of enhancing phagocytosis; eg. antibodies.

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Opsonization

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the coating of an antigen or particle ( e.g., infectious agent) by substances such as antibodies, that facilitate uptake of the foreign particle into a phagocytic cell.

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Polymorphonuclear cell (PMN)

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also known as a neutrophil or granulocyte, a PMN is characterized by a multilobed nucleus; PMNs migrate from the circulation to a site of inflammation by chemotaxis and are phagocytic for bacteria and other foreign particles. It is part of the innate immune system.

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T-cell (also T-lymphocyte)

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A defense cell that participates in a variety of cell-mediated immune reactions

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TH (helper) or CD4 cell

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A T-lymphocyte which has a molecular marker on its surface called “CD4” and functions to help or accommodate immune reactions such as sensitization of T or B lymphocytes by antigens.

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Ts (suppressor) or CD8 cell

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A T-lymphocyte which has a molecular marker on its surface called “CD8” and functions to suppress excessive immune reactions. The helper and suppressor T cells act in unison to modulate or control immunity.

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