Learning Exercise - Microorganisms Flashcards
(36 cards)
With regards to prokaryotes, briefly describe each:
Nuclear membrane
Chromosomes
Cell replication
Energy production
Specialized organelles
Nuclear membrane: absent
Chromosomes: one, circular
Cell replication: binary fission
Energy production: on the cytoplasmic membrane
Specialized organelles few (e.g. ribosomes)
With regard to eukaryotes, briefly describe each:
Nuclear membrane
Chromosomes
Cell replication
Energy production
Specialized organelles
Nuclear membrane: present
Chromosomes: multiple, linear
Cell replication: mitosis
Energy production: in mitochondria
Specialized organelles: several
What is meant by “antigenic group”, and how are groups often designated?
organisms possessing a major antigen that may be common to more than one species of the genus; usually designated by capital letters.
Describe the major shapes and arrangements of bacteria cells.
coccus: spherical
bacillus: rod or cylindrical
coccobacillus: short, plump bacillus which resembles a coccus
coryneform or diphtheroid: club shaped or chinese letter shape
pleomorphic: an organism that commonly has various distinct forms
spirochete or spirillum: spiral or corkscrew shape
(not usually visible by the Gram stain method)
arrangement:
Single - no particular arrangement
Pairs - division on one plane; daughter cells remain paired
Chains - division on one plane, perpendicular to the long axis of the chain; cells remain attached “end-to-end”
Clusters - division on three planes
Palisades - “picket fence”, division on one plane perpendicular to the short axis of the chain (bacilli only)
What is meant by “antigenic type”, and how are types often designated?
organisms possessing a specific antigen that is common to only very limited, closely related organisms (such as members of an antigenic group); usually designated by numbers.
What are the major components of the bacterial cytoplasm and what is the overall function of those components?
Cytoplasm:
Composition – thick, aqueous, elastic
(a) Cell sap (e.g. water, nutrients, storage granules, etc.)
(b) Genetic material and mechanisms (DNA, RNA, ribosomes)
(2) Function: Metabolism and replication
What are the major components of the bacterial cytoplasmic membrane and what are the overall functions of those components?
Cytoplasmic membrane:
Components:
(a) Phospholipid bilayer – Hydrophilic “heads” and hydrophobic “tails” affect movement of aqueous materials through the membrane
(b) Proteins – some function as porins (proteins that form channels through which large molecules can pass) and others as enzymes
Functions:
(a) Selective permeability – Controls transport of most compounds entering and leaving the cell
(b) Site of energy production
(c) Site of synthesis and transport of peptidoglycan, teichoic acids, and outer membrane components
(d) Site of secretion of extracellular hydrolytic enzymes
What are the major overall functions of the bacterial cell wall?
Function
(a) Shape and rigidity
(b) Provides protection from the environment and from some antimicrobic agents
(c) Certain molecules are used in the attachment to tissue cells
(d) Site of antibody attachment to major cell antigens
What is the metabolically dormant, heat resistant structure within the cytoplasm of certain gram-positive bacteria, and what is its function?
An endospore
Survival of adverse environmental conditions (resists heat, chemicals, and irradiation). Spore may be viable for years.
What is the mucoid (slimy) material surrounding certain bacterial cells and what is its function?
Capsule
(1) Composition: Polysaccharides
(2) Function
(a) Resistant to phagocytosis
(b) May “hide” surface antigens
(c) Sometimes assists in attachment (dental plaque)
What are the thread-like structures on the exterior of bacteria cells and what is their composition?
What are the functions of these structures?
Flagellum
(1) Composition: protein
(2) Function:
(a) Motility – propel the bacterium; provide locomotion
(b) Moves toward a favorable environment and away from adverse ones: Types: Chemotaxis; Phototaxis
(3) Spirochetes move by means of axial filaments, bundles of fibrils arising at ends of cell beneath outer sheath and spiral around the cell – causes corkscrew motion
Describe the components and structure of the gram-positive cell wall, including details of peptidoglycan.
In a gram-positive cell wall, the concentration of peptidoglycan is higher than in gram-negative.
(a) Peptidoglycan (60 - 80%): Alternating units of N-acetylglucosamine and N-acetylmuramic acid cross-linked by short peptide (amino acid) chains
(b) Teichoic acid strands connect to cytoplasmic membrane (Usually long chain glycerol or ribitol connected with phospholipid bridges)
(c) Protein inclusions are less frequent than in gram-negatives
Describe the components and structure of the gram-negative cell wall, including details of the “outer membrane” and their significant roles/functions.
(a) Peptidoglycan (10 - 20%)
(b) Lipoprotein layer creates a periplasmic space between peptidoglycan and the “outer membrane”. Site of certain enzymatic processes
(c) “Outer Membrane”
i. Phospholipid bilayer
ii. Pore proteins
iii. Lipopolysaccharides – Lipid with repeating units of various combinations of carbohydrates
♦ The “O” antigen (i.e. “cell wall antigen”) in antigenic tests of gram-negatives
♦ Site of Lipid A, the endotoxin molecule
A clump of a few million identical bacteria originating from the same bacterium is called a __________.
a colony
Most medically significant bacteria will reproduce about every __________ minutes under optimal conditions.
30 to 60 minutes; some 15-30 hours
Describe the types of oxygen utilization.
(a) Aerobic – requires atmospheric oxygen (~21%)
(b) Microaerophilic – requires reduced oxygen concentration (5-10%)
(c) Anaerobic – requires absence of oxygen
(d) Facultative – can grow in presence or absence of oxygen
What are the optimal temperature, pH, CO2, and humidity for growth of typical medically significant bacteria?
Temperature: 35°C (optimal)
pH: 6.8 to 7.4 (optimal)
Humidity: 60-80% (Water comprises about 70% of cell volume)
CO2 – Most medically significant bacteria do not require increased CO2, but some bacteria need 5 to 7% CO2
When compared to “typical bacteria,” what are the major characteristics that are different for those designated in class as “Atypical” bacteria? Why might this be significant to laboratory diagnosis of disease?
- Cell sizes: very small (0.1 to 0.3 um)
Cell characteristics
a. Metabolically limited - Some are obligate, intracellular parasites
b. Modified cell wall structures, if present (Mycoplasma has no cell wall)
c. Complicated or modified reproductive method
Laboratory cultivation requires living host (e.g. tissue culture, embryonated egg, etc.) or special highly enriched media
Mold cells that are multicellular long filaments are called ____________. When these cells/structures grow in a mass, they are referred to as _____________.
Hyphae
Mycelium
Reproductive forms of molds typically grow on ___________. (what structure)
Reproduce by forming spores on reproductive hyphae.
True/False.
Molds typically grow on artificial media similar to that used for bacteria, except that the media usually contains antibiotics to inhibit viruses. [If false, what is needed to make it true?]
False
Fungus can be grown on artificial media similar to that used for bacteria however the antibiotics are to inhibit bacteria growth during longer growth periods.
Describe a virus?
(type of organism, size, reproduction, etc.)
Viruses are not considered to be living organisms; however, taxonomic organization is similar to other microbes as if it were “Kingdom Virus”
Virus description:
a. Obligate, intracellular parasite
(1) Takes control of the host cell
(2) Requires metabolic processes of living cell to reproduce virus
b. Contains only one type of nucleic acid (RNA or DNA), not both
c. Unaffected by most antibiotics which are effective against bacteria (due to differences in bacterial cell morphology and structure vs virus)
Virus size: 18 to 300 nm (0.018 to .3 um) [some up to 14,000 nm in length]
What is the inner-most structure of the virus, what is it composed of, and what is its function?
Core
(a) Composition: nucleic acid (DNA or RNA, but not both)
(b) Function: genetic information
What is the structure found on the exterior of only certain viruses; what is its structural composition, and what are its primary functions?
Envelope
(a) Composition:
i. Lipid bilayer acquired from host cell or nuclear membrane
ii. Glycoproteins (“spikes”) – site for attachment and serve as antigens
(b) Function:
i. Lipid bilayer provides general protection from the environment
ii. Proteins are primary site of attachment to host cell surface
iii. Proteins serve as antigens during infection and as site for antibody attachment
