Micro study guide 1

What is a prokaryote?

simple, single-celled organism that lacks a nucleus and membrane bound organelles

What substance forms many bacterial walls and consists of glycosaminoglycan chains interlinked with short peptides?

peptidoglycan

What structure does penicillin target to disrupt the integrity of the bacterial cell wall?

peptide cross links

IDK just know this

What is a bacterial chromosome?

single, large, circular double-stranded DNA molecule that contains all genetic information required by a cell

What is a plasmid?

small, circular, double stranded DNA that is duplicated and passed to offspring; may encode antibiotic resistance, tolerance to toxic metals, enzymes, and toxins

Where are plasmids and bacterial chromosomes located within a cell?

both within the cytoplasm of the cell; chromosome specifically within nucleoid

What is transcription?

synthesis of mRNA from DNA

What is translation?

synthesis of proteins from mRNA

Why can transcription and translation occur simultaneously within the prokaryotic cell?

prokaryotic cells lack a membrane bound nucleus, so all components needed for synthesis are located in cytoplasm allowing cell to make proteins quickly

Briefly explain endospore lifecycle

2 phase life cycle: shifts between vegetative and endospore

Which bacterial generas produce endospores?

bacillus and clostridium

Which bacteria is known to cause outbreaks of diarrhea in hospitals and nursing homes?

Clostridium difficile

Will bleach-free disinfectants kill endospores?

naur (no)

Which type of bacteria has a thick layer of peptidoglycan that forms a single layer around the cell?

Gram positive bacteria

During a gram stain, what color will gram positive bacteria appear under a microscope? Why?

Purple; thick peptidoglycan layer retains crystal violet stain

Describe the steps involved in performing a gram stain

1. add crystal violet - 10 sec- rinse

2. add gram’s iodine - 10 sec - rinse

3. decolorize with 95% ethanol until colorless- rinse

4. add safranin - 10 sec - rinse

5. air dry or blot

Which step in the gram stain process if most critical and why?

third step: decolorize w/ 95% ethanol;

most affected by technical variations in timing / reagents

When viewed under a microscope, which gram-positive bacteria appear as cocci in clusters or “bunches of grapes”?

staphylococcus

When viewed under a microscope, which gram positive bacteria appear as cocci in pairs or chains?

streptococcus

How would listeria look after a gram stain when viewed under a microscope?

purple / gram positive and rod shaped

Does listeria produce spores?

naurrrr (no)

What is pleomorphism?

bacteria presents in various forms and shapes

Why is pleomorphism extreme in the mycoplasma genus of bacteria?

no cell wall- can change their shape

What are the 6 I’d of culturing microbes?

Inoculation

Incubation

Isolation

Inspection

Information gathering

Identificatoin

What is inoculation?

introduction of a sample into container of sterile media

What is incubation?

provide conditions for optimal growth, making sure you have enough microbes in sample

What is isolation?

Getting a pure culture of the microbe you’re interested in

What is inspection?

looking at colonies and microscopic characteristics of the microbe you collected

What is information gathering?

biochemical, immunologic, and genetic testing to confirm genus of microbe and identify the species

What is identification?

assigning a specific name to the microbe

What is synthetic media?

contains pure organic and inorganic compounds in an exact chemical formula

What is non-synthetic media?

contains at least one ingredient that is not chemically definable- organic extracts

What is general purpose media?

grows broad range of microbes; usually non-synthetic, nutrient agar and broth, peptone water, etc

What is enriched media?

contains complex organic substances such as blood, serum, hemoglobin, or special growth factors required by fastidious microbes

What is selective media?

contains one or more agents that inhibit growth of some microbes and encourage growth of desired microbes

What is differential media?

allows growth of several types of microbes and displays visible differences among desired and undesired microbes

Which specific medium would be best to isolate pathogenic Staphylococci?

mannitol salt agar

Describe mannitol salt agar

selective and differential; turns yellow if organism metabolizes mannitol, helping differentiate between S. aureus (yellow) and S. epidermidis (red)

Why is the growth curve in a bacterial culture closed?

they’re placed in a system with finite nutrients and space without ability to remove waste products

What are the 4 phases in the microbial growth curve?

lag phase

exponential growth (log) phase

stationary phase

death phase

Describe the lag phase of the microbial growth curve.

“flat” period of adjustment, enlargement, and synthesis of DNA, enzymes, ribosomes; little growth

Describe the exponential growth (log) phase of the microbial growth curve.

period of maximum growth that will continue as long as cells have adequate nutrients and a favorable environment

Describe the stationary phase of the microbial growth curve.

rate of cell growth equals rate of cell death- caused by depleted nutrients and O2, excretion of organic acids and pollutants

Describe the death phase of the microbial growth curve.

as limiting factors intensify, cells die exponentially in their own wastes

What is the average period of time it takes to complete the microbial growth curve?

about 4 days

Which gram positive bacteria stain like gram negative bacteria? Why?

actinomyces, corynebacterium, mycobacterium, and propionibacterium: cell walls are sensitive to breakage during cell division

bacillus and clostridium: decreased peptidoglycan during periods of growth

Which bacteria responds best to acid-fast staining?

myobacteria

Which groups of bacteria are considered obligate intracellular parasites?

rickettsias and chlamydias

How are obligate intracellular parasites different from non-obligate intracellular bacteria?

cannot serve or multiply outside of a host cell

cannot carry out metabolism on their own

List the 4 main fungal divisions (based on spore type)

zygomycota, ascomyota, basidiomycota, chytridomycota

Which fungal division does not cause human disease?

chytridomycota

Give an example of the zygomycota fungal division

rhizopus (bread mold)

Give an example of the ascomyota fungal division

penicillium, aspergillus (resp. infection), saccharomyces (yeast for bread and beer), trichiophyton (ringworm), Candida albicans, stachybotrys (toxic black mold)

Give an example of the basidiomycota fungal division

cryptococcus neoformans

What are the two morphologies in which microscopic fungi exist?

yeasts: unicellular round/oval budding cells, asexual production

hyphae: molds; long filamentous cells

yeast

hyphae

What is the difference between primary and opportunistic fungal pathogens?

primary: can exist in both yeast and mold forms (dimorphic)

opportunistic: happen secondary to weakened immune system

Give examples of primary fungal pathogens

blastomyces, histoplasma, coccidioides, paracoccidioides, sporothrix

Give examples of opportunistic fungal pathogens

cryptococcus, candida, aspergillus, penicillium, zygomycetes, trichosporon, fusarium

List the 2 examples of marine algae toxins that can cause food poisoning and the marine life each condition is associated with.

paralytic shellfish poisoning- eating exposed clams or other invertebrates

ciguatera fish poisoning- algal toxins that have accumulated in reef fish such as barracuda and moray eel

What are the two protozoan stages?

Trophozoite- motile feeding stage

cyst- dormant resistant stage

What area the protozoan groups based on?

locomotion and reproduction

List the protozoan pathogens associated with the Mastigophora group

flagellates; trypanosoma crudi (chugs disease), leishmania, Giardia lamblia, trichomonas vaginalis

What are the two groups of parasitic helminths?

Flatworms and roundworms

Describe flatworms

parasitic helminth that is flat (thin, segmented body plan), does not have definite body cavity, digestive tract is a blind pouch, has simple excretory and nervous systems subdivided into cestodes and trematodes

List and describe the two subdivisions of flatworms

cestodes (tapeworms)- long, ribbon like

trematodes (flukes)- flat, ovoid

Describe roundworms (nematodes)

parasitic helminth that is round (elongate, cylindrical, unsegmented body plan), has a complete digestive tract, a protective surface cuticle, spines and hooks on mouth, and excretory and nervous systems are poorly developed

What type of helminth is the pinworm?

roundworm

What do enveloped viruses have that naked viruses lack?

an envelope around the capsid

What are the 6 stages of virus replication? describe each

absorption- attachment to cell surface

penetration- via fusion or endocytosis, nucleic acid is released

uncoating- release of viral capsid and RNA into cytoplasm

duplication/synthesis- take control of cell’s metabolism and machinery, causing cell to synthesize basic components of new virus

assembly- nucleocapsid and envelope are formed

release- virus bud off membrane, virion ready to infect other cells

What is a cytopathic effect?

virus-induced damage to host cells that alter their microscopic appearance

List examples of cytopathic effects caused by viruses

changes in size and shape, intracellular chages

cytoplasmic or nuclear inclusion bodies composed of damaged cell organelles or compact mass of viruses

multiple cells fuse to form one large multinucleate cell- syncytium

cell lysis/death

alter DNA to transform cells into cancerous cells

What type of infections do prions cause? How are they spread?

transmissible spongiform encephalopathies (TSEs)

direct contact, contaminated foods

What is the name of the rapidly progressive neurodegenerative human prion disease?

Creutzfeldt-Jakob disease

What is a prion?

misfolded protein that does not contain nucleic acid

Which microbes have highest resistance to control?

prions and bacterial endospores (bacillus, clostridium)

What is the goal of sterilization?

destroy endospores

Define microbiostatic

any process that temporarily prevents microbes from multiplying

Define microbicide

any chemical agent that kills pathogenic organisms

Which microbicidal agent is considered a sterilizing agent?

sporicide bc it can kill endospores

Define sanitization and give an example

any cleansing technique that mechanically removes microbes;

dishwashing

Define degermation and give an example

any process that reduces number of microbes on human skin;

surgical hand scrub

define antisepsis and give an example

process that uses chemical agents on the skin to destroy or inhibit vegetative pathogens;

antibacterial soap or using iodine preoperatively

Define disinfection and give an example

any process that destroys vegetative pathogens but not endospores on inanimate objects or surfaces;

5% bleach or boiling water

Define microbial death

permanent loss of reproductive capability, even under optimal growth conditions

List the factors that can affect an antimicrobial agent’s mechanism of action

number of microbes, nature of microbes in population, temperature and pH of environment, concentration of agent, mode of action, and presence of solvents, organic matter, or inhibitors

What are the four cellular targets that antimicrobial agents aim to destroy?

cell wall, cell membrane, cellular synthetic process of proteins and nucleic acids, protein structure and function

Which antimicrobial agents are most effective for targeting cell wall and why?

antibiotics, detergents, alcohols- interfere with synthesis of cell wall

Which antimicrobial agents are most effective for targeting cell membrane and why?

surfactants- lower surface tension of cell membranes

Which antimicrobial agents are most effective for targeting cellular synthetic process of protein and nucleic acid? why?

antibiotics and chemicals- interfere with DNA and RNA function

radiation- gamma and UV cause mutations that permanently inactivate DNA

Which antimicrobial agents are most effective for targeting protein structure and function and why?

heat- coagulation by moist heat can denature proteins

chemicals- can coagulate proteins

Differentiate heat sterilization and disinfection

heat sterilization destroys endospores, disinfection does not

Is moist heat or dry heat more effective for microbial control?

moist heat

What is a common form of moist heat used in hospitals and medical offices to sterilize glass, cloth, metal, and certain cloth and rubber?

autoclave

What is desiccation? Is it an effective method of sterilization?

gradual removal of water from cells leading to metabolic inhibition

naur, not an effective microbial control- cells retain the ability to grow when water is reintroduced

Differentiate ionizing and non ionizing radiation

ionizing- deep penetrating power, breaks DNA (gamma, x-rays, high speed electrons)

non-ionizing- little penetrating power, causes DNA mutations by formation of abnormal bonds (Uv light)

What is filtration?

mechanical removal of microbes by passing a gas or liquid through a filter

Give examples of substances that are best sterilized by filtration

heat sensitive liquids like blood products, IV fluids, IV drugs

hospital isolation units through HEPA filters