microorganisms classification taxonomy Flashcards
why is globalisation an important characteristics?
more opportunities for pathogens to spread from one location to the other
what is not included in the tree of life and why?
viruses and prions - they are infectious particles and do not fit the criteria for a living organism
when writing the name of an organism which is the only part with a capital?
genus
how is placement done on tree of life?
there are stains that are widely used in organism identification instead of classification - use DNA (not a stain), gram stain, cell shape, endospore, atmospheric preference, fastidiousness and key enzymes
what are bacteria?
they are single celled organisms that lack a membrane bound nucleus and are prokaryotes
what is the flagella?
it is responsible for locomotion - the number and location can vary - mono, lopho, amphi and peritrichous - used to propel the pathogens e.g. e. coli from urethra to bladder and for identification
what are the pilli or fimbriae?
they are structures that are exposed to the extracellular space that aid adhesion to host cells and colonisation - adhesion - invasion - infection and can act as a virulence factor
what are examples of pilli?
pap pilli in uropathogenic E coli, opacity protein of Neisseria gonorrhoea - can adheres to a specific substrate on cell surface - contributes to tissue tropism of certain pathogens
what is the capsule or the slime layer?
it is a polysaccharide tightly adhered if capsule or loosely if slime, material that protects the bacteria from phagocytosis, dessication and antibiotics
what are biofilms?
community of bacteria surrounded by extracellular polymeric substances
what are endospores?
metabolically inert forms of bacteria that are resistant to many forms of environmental stress - UV, temperature, antiseptics and dessication. Bacillus and Clostridium are genus examples
what is the difference between gram negative and positive bacteria?
outer membrane in gram negative
what are the four cell walls encountered in bacteria?
gram positive, negative, mycobacterial and no peptidoglycan (atypical)
what are examples of gram negative and positive?
negative: E coli and neisseria
positive: strepto and staphylococcus
what would you use for mycobacterial cell wall?
acid fast staining
what is an example of mycobacterial and no peptidoglycan cell wall?
no peptidoglycan - chlamydia
mycobacterial - mycobacterium
how can bacteria be divided into two or three groups?
based on ability to retain crystal violet- iodine dye complex - following acetone or alcohol treatment
how would gram positive and negative bacteria appear with a crystal violet iodine complex dye?
positive - retain the complex - blue/purple
negative - loss of complex so red/pink
in mycobacteria in colourless - stains are unable to penetrate mycolic acid layer
how do bacteria replicate?
through binary fission - vertical gene transfer
how do bacteria acquire DNA?
through horizontal gene transfer which is important for resistance and virulence factors - transduction, transformation and conjugation
what is the process of horizontal gene transfer?
replication of the circular prokaryotic chromosome begins at the origin of replication and continues in both directions, the cell begins to elongate and FtsZ proteins migrate towards the midpoint of the cell. The duplicated chromosomes separate and continue to move away from each other towards the ends of the cell. FtsZ proteins form a ring around the periphery of the cell of the midpoint between chromosomes. The FtsZ ring directs the formation of a septum and the plasma and cell wall materials accumulate. The cell pinches in two and the FtsZ disperses throughout the cytoplasm of the two daughter cells
how do acquisition of DNA occur with bacteria chromosomes?
the pilus retracts, cell pairs are stabilised and the F plasmid is nicked in one strand, transfer of one strand from one cell to the other and the F plasmid is simultaneously replicated in the first cell. Synthesis of the complementary strand begins in the recipient cell and there is completion of the DNA transfer and synthesis - cells separate
how does acquisition of DNA occur when there is an integrated F plasmid?
the F plasmid is nicked in one strand and transferred followed by chromosomal DNA - synthesis of second strand in recipient and donor cells
what is the basis of transformation?
there is binding DNA and then the uptake of single stranded DNA and then RecA-mediated homologous recombination
what is the basis of transduction?
the transducing particle attaches to host cell and injects DNA then there is homologous recombination
what are fungi?
they are eukaryotes and most have a chitin cell wall - disease causing can be yeasts such as saccharomyces cerevisiae, filamentous such as aspergillus or dimoprhic - yeast and mould
what is oral candidiasis?
an example of dysbiosis
what is the cause of filamentous mould infections?
common is superficial infections such as ringworm or athletes, uncommon is severe infections such as aspergillosis and mucormycosis
what is the replication method of moulds?
sexual or asexual depending on spores
what happens in germination?
mycelia form and sometimes if close proximity and mating then extensions between them called gametangia
what is the life cycle through sexual and asexual reproduction of moulds?
germination, plasmogamy, karyogamy, meiosis and germination for sexual
asexual - germination, spores, mitosis
what are the subtypes of parasites?
protozoa or helminths
what are protozoa?
they are unicellular eukaryotes - they can be intestinal (cryptosporidium, entamoeba or giardia) or non intestinal (trypanosoma, leishmania or plasmodium)
what are helminths?
they are multicellular eukaryotes that can be intestinal (enterbius, ascaris or taenia) or non intestinal (schistosoma)
what is the replication of parasites?
can be complex - rely on multiple hosts to complete the life cycle, may include cyst formation for survival and sexual or asexual forms
what are viruses?
they are obligate intracellular parasites that every class of organism suffers from - they are a nucleic acid core (DNA or RNA) covered by a protein coat and some have a lipid membrane
what is a retrovirus?
one that makes RNA into cDNA using reverse transcriptase
what is the life cycle of the virus?
attachment through a specific receptor using tropism, penetration through endocytosis or membrane fusion, uncoating where the viral contents are released, biosynthesis where viral RNA entere nucleus and is replicated by viral RNA polymerase, assembly where new particles are made and release which may or may not kill host cell
what are the early viral proteins produced?
polymerase and intergrase which allows genomic replication
when are the structural proteins made and what are they commonly?
as late viral proteins and are capsid, surface proteins and assembly of virion
how does release occur?
via budding or cell lysis depending on characteristics - nature of the RNA or DNA, symmetry of the capsid, presence or absence of an envelope and the dimensions of the virions and capsid
what are prions?
they are misfolded proteins that unlike viruses have no genetic material - they can be inherited, spread via contaminated material or occur spontaneously
what is the basis of a prion condition?
the aggregation and misfolding of native proteins - chain reaction
what are examples of prion conditions?
scrapie, CJD, kuru and BSE
