Micro Flashcards
What is mycology?
The scientific study of fungi
What are some characteristics of fungi?
Eukaryotic Non-motile, rigid cell wall (chitin) Can be unicellular(yeasts) or multicellular (moulds) Saprophytes (feed of decomposing matter) or parasites Aerobes, some faculties anaerobes. Complex repro Classes based on sexual spores Insensitive to antibacterial antibiotics
Describe chitin and where it is found.
Chitin is a protective layer of chains of N-acetylglucosamine which is highly resistant to enzymatic breakdown. It is found within the fungal cell wall.
Discuss yeasts.
Type of fungi. Unicellular, spherical cells, 3-5um.
Reproduce asexually by budding, moist/mucoid colonies, facultive anaerobes.
Discuss moulds.
Filamentous fungi eg. Penicillin, microsporum.
Multicellular filaments, 2-10um wide (Hypae), can be septate(divided by cross walls), nonseptate (coencytic) or vegetative or aerial.
Reproduce sexually(spores) or asexually(condida)
Aerobic
Intertwined mass hyphae (mycelium/thallus)
What do septate hyphae possess that nonseptate don’t?
Septa-cross walls
Penicillin is septate, rhizopus is nonseptate
What are the two types of functional fungal hyphae? Briefly describe the cycle between the two.
Vegetative hyphae, reproductive hyphae
VH present on surface, fruiting bodies begin to grow and produce spores (RH), spores germinate into germ tube, hypha and then become vegetative hyphae again.
What temperatures are required for dimorphic fungi to grow in vitro and in Vivo?
In vitro - 25degrees Celsius
In Vivo - 37degrees Celsius
True or false. Many fungal species have a full lifecycle with both asexual and sexual states that are separated in time.
True
What is the sexual stage of a fungi lifecycle called?
Telomorphic.
Meiosis occurs producing meiospores.
What is the asexual period of a fungi lifecycle called?
Anamorphic.
Mitosis produces mitospores.
What are some types of asexual Filamentous fungal spores (mould)?
Sporangiospores.
Conidia.
What are the four main fungal classes?
Zygomycetes, ascomycetes, basidiomycetes, deuteromycetes.
What is pathogenicity?
Capacity to produce disease.
To cause disease a fungus must….
Enter host, multiply in host tissue, resist or not stimulate host defence, damage host.
What are the four forms of fungal disease in animals?
Infectious-parasitic fungi, mycoses.
Toxigenic-saprophyte or plant, mycotoxicoses.
Allergenic-sensitisation, mainly spores.
Effects on non-toxic spoilage-feed refusal, nutritional deficiencies.
What are the stages of fungal disease diagnosis?
The first 4 are the main forms.
- Clinical behaviour and appearance of lesions.
- Cytology of exudate/tissues-gram stain, KOH, etc.
- Fungal culture and appearance-macro and microscopic.
- Histopathology-gram stain, H&E, Etc.
- Immunofluorescence tests
- Molecular methods
- Skin tests
- Serology
- Animal inoculation
What are the differences between the microscopic morphology of yeasts and moulds?
Yeasts may have buds, capsules and germ tube production.
Moulds have hyphae, sexual spores or asexual conidia.
What is the term for fungal diseases in animals?
Mycoses.
These can be systemic/deep, cutaneous and subcutaneous.
What are the three domains of life?
Eukarya, bacteria, archaea
What are bacteria and archaea?
Prokaryotes-before nucleus
What is microbiology?
The study of micro organisms.
True or false, viruses are acellular?
True
True or false. Fungi and Protozoa are both eukaryotes?
True
What person used the term cells to describe the box-like structure he saw in cork tissue?
Robert Hooke.
Anton van Leeuwenhoek developed what?
High powered lenses
What did Louis Pasteur do?
Disproved spontaneous generation through development of S shaped flasks (kept microbes out).
What did Robert Koch do?
Established criteria necessary to prove causal relationship between a specific organism and disease (Kochs Postulate).
Describe the steps in Kochs postulate.
- Specific microorganism must be present in every case of the disease.
- Specific microorganism must be isolated and grown in pure culture.
- Inoculation of the pure culture must cause the disease in susceptible animals.
- The specific organism must be observed in and recovered from the experimentally diseased animal and its identity confirmed.
What were the limitations of Kochs postulate?
Noninfectious disease, mixed infections, uncultivable microbes, diseases with predisposing factors, diseases with carrier state, disease by opportunistic agent.
More holistic view is required in these situations - agent, host and environment.
Describe the characteristics of prokaryote cells.
DNA is a single molecule not in the nucleus. No nucleus.
No membrane bound organelles. Cell wall.
Usually
Describe the characteristics of a eukaryotic cell.
DNA in chromosomes in a nucleus. Membrane bound organelles. >10um diameter. Replicate by mitosis, gametes by meiosis. 80S and 70S ribosomes.
Membrane bound, no cell wall, mitochondria.
What is a cell envelope?
Cytoplasmic membrane surrounded by a rigid cell wall.
Membrane is phospholipids and proteins, semipermeable.
Wall is mainly peptoglycan, rigid, unique to prokaryotes.
What is an antigen?
Foreign molecule that induces an immune response.
Describe the structure of bacteria.
Prokaryotic cell. Cell envelope consisting of glycocalyx, cell wall and membrane. Cytoplasm with ribosomes. Nuclear material in centre. Flagellum and pilli may be present.
Bacteria divide by gram reaction on cell wall peptidoglycan. True or false?
True.
What are the differences between a gram positive and gram negative cell envelope?
Positive-2 layers, thick peptidoglycan, may have techoic aids.
Negative-3 layers, thin peptidoglycan, outer LPS(endotoxins and lipoproteins).
What are some forms of appendages that may be present on bacteria?
Capsule-streptococcus, anthrax, firm gelatinous coat of carbs and proteins, protective and antigenic. Outermost layer of cell.
Flagella-clostridia, thin long whip like structure, flagellin protein, motility.
Pilus/Fimbria-ecoli, gram negative, finer and shorter than flagella, pilin protein, adhesion, conjugation.
What is a bacterial specific form of nuclear material?
Plasmid.
Small, autonomous replicating circular DNA.
Can be shared between organisms via conjugation pilus.
If a bacterial cell has a ebdospore or spore present it is gram?…..
Positive
Describe the forms of bacterial identification.
Direct microscopic examination,
Culture (MATT, media, atmosphere, temp/humidity, time)
Immunological methods-serotyping, immunoassays.
Molecular methods-pcr
Phage typing
Describe the microscopic morphology of bacteria.
Size-0.2-2um wide, 1-5um long.
Shape and arrangement-Cocci or bacilli.
Gram reaction-positive or negative, determined by peptidoglycan.
Capsules or spores.
What are the different names of cocci arrangements?
Cocci(spherical) can be paired (diplo), chains(strepto), staphylococci(clusters), sarcinae(cubical).
What are the different forms of bacilli arrangement?
Bacilli (cylindrical) can be coccobacilli(short), fusiform(tapered ends), Filamentous, vibrio or spirella(curved).
What is the term used for a spore that is located at or towards the end of a cell.
Terminal. Sub terminal if towards the end, terminal if at end, bulging terminal if bulging.
What are the stages to making and heat fixing a smear?
Apply bacteria to plate using inoculating needle. Spread out mixture and allow to air dry. Once dry heat fix by passing over flame 3-4 times.
What are the 4 steps to the gram stain technique?
- Crystal violet
- Grams iodine
- Alcohol(de colouriser)
- Safranin (red dye)
How do bacteria replicate?
Binary fission.
Circular chromosome replicates, cell elongates, chromosomes move apart and cell divides leaving 2 daughter cells.
Cells may remain attached resulting in groupings eg. Streptococcus, sarcina, irregular clusters.
What are the two types of bacterial variants?
Phenotypic, genotypic.
Genotypic can be mutation, recombination, transposition.
Recombination can be transduction, conjugation, transformation.
An organism of the genus bacillus will be ….. While an organism if the genus staphylococcus will be ….
Rod shaped
Spherical
The process whereby DNA from donor bacterium becomes incorporated into nucleic acid of a phage and is transferred to susceptible recipient bacterial cells is called?
Transduction
What is recombination?
Exchange of DNA between bacteria.
What is transposition?
Relocating of portions of DNA in the genome mediated by transposable elements.
What is transformation?
Uptake of naked DNA segment.
What is conjugation?
Plasmid mediated transfer.
What is a mutation?
Change in chromosomal DNA.
What are some nutritional requirements of bacteria?
C, N, H, growth factors
What is a common culture media used to grow bacteria?
Nutrient agar, blood agar, macConkey.
Describe the growth of bacteria in liquid media.
Lag phase-no increase in number, adaption time.
Exponential phase-calls divide at constant rate via binary fission. Best stage for staining etc.
Stationary phase-decreased growth rate until cell number stays constant. Exhaustion of essential nutrients or accumulation of toxic wastes.
Death/decline phase-cells die.
What kind of bacteria congregate at the surface of broth?
Aerobic
What kind of bacteria congregate at the base of broth?
Anaerobic
What kind of media congregate across the whole broth but are more concentrated at the surface?
Facultive
What kind of bacteria congregate slightly below the surface of broth?
Microaerophilic
What kind of bacteria spread evenly across the whole broth?
Aero tolerant anaerobes
A psychrophile grows best at what temperature?
4 degrees Celsius
A mesophile grows best at what temp?
39 degrees Celsius
A thermophile grows best at what temperature?
60
A hyper thermophile grows best at what temp?
88
The scientific method is a process for experimentation that is used to explore observations and answer questions. Review the steps of the scientific method.
Ask a question, do background research, create hypothesis, create procedure with specific directions for experiment, observe closely and record data, organise and evaluate data, create conclusion, summarise experiment through abstract, present and communicate your results
What growth characteristics can be used to describe colonies?
Shape, size, elevation, edge, colour, opacity, haemolysis.
What are some target sites of antibiotics in bacteria?
Cell wall synthesis or integrity, DNA sysnthesis, RNA polymerase, protein synthesis, phospholipid membrane
What are the two forms of microbial associations?
Symbiotic-organisms live in close nutritional relationships, required by one or both members.
Non-symbiotic-organisms free living, relationship not required for survival.
All microbes are bad and cause disease. True or false?
False.
What are the three forms of symbiotic relationships?
Mutualism-obligatory, dependent, both members benefit.
Commensalism-commensal benefits, other member not harmed.
Parasitism-parasite dependent on benefits, host is harmed.
What are the two forms of non-symbiotic associations?
Synergism-members cooperate and share nutrients.
Antagonism-some members inhibited or destroyed by others.
When is normal resident flora established?
Birth.
Where does normal resident flora exist on humans?
Surfaces exposed to the environment-skin and adjacent external ear and eye. Mucous membranes.
NOT in sterile tissue or fluids.
What area transient flora?
Short term flora, cling temporarily and don’t grow.
What are opportunistic (secondary) pathogens?
Cause disease when host is compromised.
Not pathogenic to normal healthy hosts.
What are true/obligate (primary) pathogens?
Microbes which can cause disease in normal healthy hosts.
What protection mechanisms does a host have against invading pathogens?
Physical barriers-skin, self cleaning, normal flora.
Innate immunity-inflammation, defensins, lysozymes
Specific immunity-antibodies, cell-mediated immunity.
What is competitive exclusion?
When normal flora excludes pathogens from body surfaces by competition.
In the absence of normal flora, pathogens can colonise and invade.
What is a virus?
Very small (17-300nm), infectious particle, an obligate intracellular parasite. Not true living cell, must have host cell to invade in order to replicate.
True or false. A virus contains only an RNA genome.
False, viruses can contain genomes of either DNA or RNA.
How and where does a virus replicate?
Replicates only in living host cells (animal, plant, bacteria)
Completely dependent on host cell metabolism and machinery for genome relocation, protein synthesis and packaging.
Does a virus have ribosomes or cellular organelles?
No
What are the two phases of virus existence?
Extra cellular-metabolically inert, transmission phase. Meta stable structures.
Intracellular phase-exploits host cells metabolic systems to replicate genome and direct synthesis of virion components.
What is a virion?
Complete infectious virus particle.
What is a nucleocapsid?
Capsid plus enclosed nucleic acid.
Describe the structure of a virus.
Particle is made of covering and central core. Covering is composed of capsid (protein coat) and envelope (not all viruses). Central core contains nucleic acid molecule and various proteins (enzymes).
In terms of a virus, what are peplomers?
Viral encoded spikes (surface receptors).
How are DNA classified?
Type of genome-DNA or RNA, single or double stranded nucleic acid, size and morphology, replication strategy, pathogenicity, sequence, immunological properties, susceptibility.
Outline the nomenclature for naming viruses?
Order-suffix is virales Family-suffix is viridae Subfamily-suffix virinae Genus-suffix virus Species-no suffix. ALL IN ITALICS.
Discuss the characteristic of the viral genome.
Either RNA or DNA, may be single or double stranded, linear or circular.
All are haploid, some are segmented.
Size between 3-300Kb
Number of proteins varies according to size.
Nucleic acid of some is infectious.
What is a dimorphic fungus?
Can exist as mould form or yeast form.
Eg. Coccidiodies, histoplasa
Give some examples of opportunistic fungus?
Candida, aspergilus.
These are different from dimorphic.
What is a common media used to grow fungi in the lab?
Nutrient agar
Describe the steps involved in streaking a plate for bacterial culture. Include explanation of principles/objectives of the method and macroscopic features of bacteria that are revealed.
Label upper half of plate with name, date, sample details.
Flame loop and pick up material to be inoculated. Spread charged loop over small surface of agar. Reflame, allow to cool. Rotate plate and streak 4 parallel lines with cooled loop each passing through initial smear. Reflame. Repeat twice more. Finally, make a streak into centre of plate, don’t touch initial inoculum. Replace lid.
Allows growth of individual colonies.
All viruses must make a way to create mRNA. True of false?
True.
How can viruses be inactivated?
Temperature-seconds at 60, minutes at 37
Radiation-nonionising, ionising
pH-strong acid or base denatures protein.
Chemical agents-detergents, oxidising, etc.
Are enveloped or non-enveloped viruses more susceptible to disinfectants?
Enveloped.
How can viruses be preserved?
Temperature-4C, or less, liquid N
Chemical agents-DMSO, glycerol, serum
Freeze drying-lyophilisation with BS or casein, reconstitute with water.
Describe the processes involved in replication of viruses.
- Attachment of virus to specific receptors in host cell
- Penetration of virus into cell.
- Uncoating or removal of protein coat from virus
- Early transcription, mRNA
- Early translation of viral proteins.
- Viral nucleic acid synthesis.
- Late transcription, further mRNA
- Late translation and synthesis of viral structural proteins.
- Assembly of progeny virus particles.
- Release of assembled particles.
How do viruses attach to host cells?
Attachment protein on surface of virus binds with cell membrane receptor.
What determines the morphological appearance of a virus?
The arrangement of surface proteins.
What are the two forms of capsid morphology?
Symmetrical or complex.
What is a virus envelope?
A host membrane derived lipoprotein that surrounds the nucleocapsid.
Acquired when virus buds through cell membrane.
Contains virus encoding proteins required for infectivity.
What does pleomorphic mean?
Not symmetrical, fluid.
In viruses, what is the matrix?
Protein layer on the inside of the envelope of virions of some families.
What are the functions of viral proteins?
Structural-protection and support, carry ligands for host cell attachment.
Non-structural-enzymes, cellular proteins (histones), other viral proteins (modify host immune response, involved in infectious cycle).
What are prions?
Proteinaceous infectious particles abt at cause degenerative nervous disorders. (Protein infection)
Disease is caused by abnormal form of a normal cell protein, found particularly in plasma membrane of nerve cells.
When prion infects it converts the normal protein to the abnormal.
