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H

  • hair follicle a structure embedded in the dermis from which hair grows
  • halophile organism that depends on high concentrations of salt in the environment to grow
  • halotolerant organism that grows in the presence of high salt concentration but does not require it
  • Hansen’s Disease chronic bacterial infection of peripheral nervous tissues caused by the acid-fast bacterium, Mycobacterium leprae ; also known as leprosy
  • hantavirus pulmonary syndrome acute lung infection by a hantavirus following inhalation of aerosols from the urine or feces of infected rodents
  • haploid having one copy of each chromosome
  • hapten a molecule that is too small to be antigenic alone but becomes antigenic when conjugated to a larger protein molecule
  • hard chancre a generally painless ulcer that develops at the site of infection in primary syphilis
  • Hashimoto thyroiditis hypothyroidism caused by an autoimmune disease affecting thyroid function
  • healthcare-associated infection (HAI) an infection acquired in a hospital or other health-care facility unrelated to the reason for which the patient was initially admitted; nosocomial infection
  • heavy chains longest identical peptide chains in antibody molecules (two per antibody monomer), composed of variable and constant region segments
  • helical virus cylindrical or rod shaped
  • helicase enzyme that unwinds DNA by breaking the hydrogen bonds between the nitrogenous base pairs, using ATP
  • helminth a multicellular parasitic worm
  • helper T cells class of T cells that is the central orchestrator of the cellular and humoral defenses of adaptive immunity and the cellular defenses of innate immunity
  • hemagglutination visible clumping of red blood cells that can be caused by some viruses, bacteria, and certain diseases in which antibodies are produced that bind to self-red blood cells
  • hematopoiesis formation, development, and differentiation of blood cells from pluripotent hematopoietic stem cells
  • hematuria condition in which there is blood in the urine
  • hemolysin class of exotoxin that targets and lyses red blood cells, as well as other cells
  • hemolytic disease of the newborn (HDN) type II hypersensitivity reaction that occurs when maternal anti-Rh antibodies cross the placenta and target fetal Rh+ red blood cells for lysis
  • hemolytic transfusion reaction (HTR) condition resulting after an incompatible blood transfusion; caused by type II hypersensitivity reaction and destruction of red blood cells
  • hemorrhagic fever with renal syndrome serious hemorrhagic fever caused by hantavirus infection
  • HEPA filter high-efficiency particulate air filter with an effective pore size that captures bacterial cells, endospores, and viruses as air passes through, removing them from the air
  • hepatitis inflammation of the liver
  • herd immunity a reduction in disease prevalence brought about when few individuals in a population are susceptible to an infectious agent
  • herpes keratitis eye infection caused by herpes simplex virus
  • herpes simplex virus type 2 (HSV-2) the type of herpesvirus most commonly associated with genital herpes
  • herpetic gingivostomatitis inflammation of the mouth and gums often caused by the HSV-1 virus
  • heterolactic fermentation process producing a mixture of lactic acid, ethanol and/or acetic acid, and CO 2 as fermentation products; the microbes that do this use pentose phosphate pathway glycolysis, which is why they generate multiple fermentation products
  • heterotroph organism that uses fixed organic carbon compounds as its carbon source
  • hexose monophosphate shunt see pentose phosphate pathway
  • Hfr cell E. coli cell in which an F plasmid has integrated into the host cell’s chromosome
  • high G+C gram-positive bacteria bacteria that have more than 50% guanine and cytosine nucleotides in their DNA
  • high-energy phosphate bond bond between the negatively charged phosphate groups that holds a lot of potential energy
  • histamine proinflammatory molecule released by basophils and mast cells in response to stimulation by other cytokines and chemical mediators
  • histones DNA-binding proteins found in eukaryotes and archaea that aid in orderly packaging of chromosomal DNA
  • histoplasmosis fungal disease caused by the dimorphic fungus Histoplasma capsulatum
  • holoenzyme enzyme with a bound cofactor or coenzyme
  • holozoic refers to protozoans that consume food particles through phagoctytosis
  • homolactic fermentation process producing only lactic acid as a fermentation product; the microbes that do this use Embden-Meyerhof-Parnas glycolysis
  • hookworm infection soil-transmitted intestinal infection caused by the nematodes Necator americanus and Ancylostoma doudenale
  • horizontal direct transmission movement of a pathogen from one host to another (excluding mother to embryo, fetus, or infant) in a population through physical contact or through droplet transmission
  • horizontal gene transfer introduction of genetic material from one organism to another organism within the same generation
  • host range the types of host cells that a particular virus is able to infect
  • HTST high-temperature short-time pasteurization is a method of pasteurization commonly used for milk in which the milk is exposed to a temperature of 72 °C for 15 seconds
  • human African trypanosomiasis serious infection caused by Trypanosoma brucei and spread by the bite of the tsetse fly
  • human granulocytic anaplasmosis zoonotic tickborne disease caused by the obligate intracellular pathogen Anaplasma phagocytophilum
  • human immunodeficiency virus (HIV) retrovirus responsible for acquired immune deficiency syndrome (AIDS) in humans
  • human papillomavirus (HPV) a group of common sexually transmitted viruses that may be associated with genital warts or with cervical cancer
  • humanized monoclonal antibodies chimeric antibodies with mouse variable regions and human constant regions
  • humoral immunity adaptive immunity mediated by antibodies produced by B cells
  • hyaluronidase enzyme produced by pathogens that degrades hyaluronic acid between adjacent cells in connective tissue
  • hybridization the joining of two complementary single-stranded DNA molecules
  • hybridoma clones of cell produced by fusing a normal B cell with a myeloma cell that is capable of producing monoclonal antibodies indefinitely
  • hydatid disease cystic echinococcosis, an infection caused by the tapeworm Echinococcus granulosus
  • hydrophilic “water loving”; refers to a polar molecule or portion of a molecule capable of strong attraction to water molecules
  • hydrophobic “water fearing”; refers to a nonpolar molecule or portion of a molecule not capable of strong attraction to water molecules
  • hypersensitivity pneumonitis (HP) type III and IV hypersensitivities in the lungs that are caused by environmental or occupational exposure to allergens such as mold and dust
  • hypersensitivity potentially damaging immune response against an antigen
  • hyperthermophile a microorganism that has an optimum growth temperature close to the temperature of boiling water
  • hypertonic medium an environment in which the solute concentration outside a cell exceeds that inside the cell, causing water molecules to move out of the cell, resulting in crenation (shriveling) or plasmolysis.
  • hyphae tubular, filamentous structures that makes up most fungi
  • hypodermis the layer of tissue under the dermis, consisting primarily of fibrous and adipose connective tissue
  • hypotonic medium an environment in which the solute concentration inside a cell exceeds that outside the cell, causing water molecules to move into the cell, possibly leading to swelling and possibly lysis

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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