Introduction Flashcards
Parasitism
A relationship in which a host provides the primary benefit to the parasite.
Mutualism
One that benefits all of the contributing parties.
Eg: Lichens consisting of fungus and algae or cyanobacterium.
Most heterogeneous subset of all living creatures
Microorganism
Prokaryotes
Without true nucleus,
Circular chromosomes with d.s. DNA w/o histones,
Single gene, only axons are present,
Nucleoli absent,
Ribosomes 70s subunit,
No organelles present,
Ribosomes present,
mRNA polycistronic with multiple shine dalagarno sequences.
Cell-cell communication mechanism aka quorum sensing (depends on production of auto inducers or pheromones that enables the bacterium to monitor its own cell population density) to regulate the transcription of genes in diverse physiological processes.
Are haploid.
Eukaryotic microorganism
Algae, Protozoa, fungi, and slime molds.
Plasmids
Extra chromosomal d.s. DNA in bacteria that are capable of replication within at least one cell line,
Can alter the virulence,
Exhibit a broad host range that allows them to convey sets of genes to diverse organisms:
Capability to adhere via adhesins,
Produce resistance to certain drugs.
Bacteriophages
Viruses capable of injecting genetic material, eg diphtherium bacterium.
Jumping genes/ transposons
Special type of d.s. DNA fragments which jump around,
Can alter the pathogenicity of bacteria.
Viroids
Naked (extra cellular form) infectious RNA molecules (small, single stranded existing as highly base paired rodlike structures, contains no protein encoding genes), produce infection in plants,
Size 246 to 375 nucleotides in length,
Totally dependent on host functions for replication,
Replicated by the DNA dependent RNA polymerase of the plant host,
Contains inverted repeated base sequences at their 3’ and 5’ ends.
Virus
Non-living/ non-cellular infectious agents,
Has either DNA or RNA with protein cover.
Virophages
Viruses that infect other viruses.
Virus- protein coat/ capsid
Glycoproteins,
Determine the specificity of interaction of a virus with its host cell,
Protects the nucleic acid and facilitate attachment and penetration of the host cell by the virus.
Viral replication
Inside the cell, viral nucleic acid redirects the host’s enzymatic machinery to functions associated with replication of the virus. Or the genetic information from the virus can be incorporated as DNA into a host chromosome. Or the viral genetic information can serve as a basis for cellular manufacture and release of copies of the virus. This process calls for replication of the viral nucleic acid and production of specific viral proteins.
Maturation consists of assembling newly synthesised nucleic acid and protein subunits into mature viral particles, which are then liberated into the extra cellular environment.
Small virus replication
Similar but requires the assistance of another virus in the host cell for their duplication. The delta agent, aka hepatitis D virus is too small to code for even a single capsid protein and needs help from hepatitis B virus for transmission.
Smallest infectious particle
Prions
Scrapie
Degenerative CNS disease of sheep.
Prions
Cellular form of the prion proteins PrPc is encoded by the hosts chromosomal DNA. PrPc- sialoglycoprotein, molecular mass 33000-35000 daltons, high content of alpha helical secondary structure i.e. sensitive to proteases and soluble in detergent, PrPc expressed on the surface of neurons via glycosylphosphatidyl inositol anchor in both infected and uninfected brains. Conformational change occurs in the prion proteins, changing it from its normal or cellular form PrPc to the disease causing conformation PrPSc implying when present in an individual, it is capable of recruiting PrPSc and converting it to disease form.
Eg: Kuru, CJD, Gerstmann-Straussler-Scheinker dz, fatal familial insomnia, BSE/ mad cow dz, vCJD.
Capable of causing chronic neurologic diseases.
Acquired human prion dz
vCJD associated with ingestion of prion infected particles, kuru, CJD.
Sporadic human prion dz
CJD unknown source.
Familial human prion dz
Great an-straussler-scheinker dz, fatal familial insomnia, CJD associated with specific mutations within the gene coding PrP.
beta pleated arrangements of protein include
Prion proteins, silk, amyloid.
Smallest infectious living organisms.
Mycoplasma: Parasitic prokaryotes, no cell wall, adaptation has resulted in incorporation of sterol into their cell membranes.
Microbial eukaryotes
Protists: are members of the following four major groups i.e. algae, Protozoa, fungi, slime molds.
Algae
Denote all organisms that produces O2 as a product of photosynthesis,
Contains chlorophyll,
Are unicellular or multicellular,
Can produce toxins that are poisonous to humans and animals.
Eg: Kelps- brown algae, several hundred meters in length;
Dinoflagellates- unicellular alga, cause algal blooms or red tides, mainly Gonyaulax species can produce neurotoxins such as SAXITOXINS or GONYAUTOXINS, which accumulate in shellfish and ingestion of these shellfish by humans results in symptoms of PARALYTIC SHELLFISH POISONING that can lead to death.
