micro final exam part 1

microbiome

is a group of microbes that live stably on/in the human body
Help to maintain good health
Can prevent the growth of pathogenic microbes
May help train the immune system to discriminate threats

Normal microbiota

is the collection of acquired microorganisms on or in a healthy human being
Begin to be acquired as newborns
May colonize the body indefinitely

Transient microbiota

microbes that colonize the body fleetingly

the three classifications of microorganisms

bacteria, archaea, eukarya

benefit of protozoa

absorb or ingest organic chemicals, phorosynthetic

benefit of algae

photosynthesis: process oxygen and carbohydrates

drawback of parasites

flatworms and roundworms

drawback of viruses

make people sick, infect people

Bacteriology

study of bacteria

mycology

study of fungi

parasitology

study of protozoa and parasitic worms

immunology

study of immunity

virology

study of viruses

gram-positive cell walls

Thick peptidoglycan
Teichoic acids

Outer membrane
Periplasmic space

gram-negative cell walls

4 rings in basal body of flagella
Produce endotoxins and exotoxins
Low susceptibility to penicillin
Thin peptidoglycan

Bacterial chromosome

circular thread of DNA that contains the cell’s genetic information

plasmids

extrachromosomal genetic elements; carry non-crucial genes
In prokarotes it contains the cells genetic information

ribosomes

Sites of protein synthesis
Made of protein and ribosomal RNA

physical requirements for microbial growth

Temperature
pH (6-7)
Osmotic pressure

biofilms

Microbial communities, form slime or hydrogels that adhere to surfaces
Bacteria can communicate cell-to-cell via quorum sensing
Bacteria secrete an inducer (signaling chemical) to attract bacterial cells
Share nutrients
Shelter bacteria from harmful environmental factors
Involved in 70% of infections and are 1000x resistant to microbes

Culture medium

nutrients prepared for microbial growth

sterile

no living microbes

Inoculum

introduction of microbes into a medium

Culture

microbes growing in or on a culture medium

Agar

complex polysaccharide, used as a solidifying agent for culture media in Petri plates, slants, and deeps. Usually not metabolized by microbes

Chemically defined media

exact chemical composition is known

Complex media

extracts and digests of yeasts, meat, or plants; chemical composition varies batch to batch (NUTRIENT BOTH AND NUTRIENT AGAR)

Phases of microbial growth

lag phase, log phase, stationary phase, death phase

lag phase

intense inactivity preparing for population growth, but no increase in population

Log phase

logarithmic, or exponential increase in population

Stationary phase

period of equilibrium; microbial deaths balance production of new cells (carrying capacity)

Death phase

population is decreasing at a logarithmic rate

plate counts

count colonies on plates that have 30 to 300 colonies

Filtration

solution passed through a filter that collects bacteria, filter is transferred to a petri dish and grows as colonies on the surface

Most probable number (MPN) method

multiple tube test, count positive tubes, compare with statistical table

Direct Microscopic Count

volume of a bacterial suspension placed on a slide, average number of bacteria per viewing field is calculated, uses special petroff-hausser cell counter

obligate aerobes

growth occurs only where high concentrations of oxygen

facultative anaerobes

growth is best where most oxygen is present, but occurs throughout tube

obligate anaerobes

growth occurs only where there is no oxygen

aerotolerant anaerobes

growth occurs evenly

microaerophiles

growth occurs only where a low concentration of oxygen has diffused (so in the middle of a tube)

sepsis

refers to bacterial contamination

Asepsis

the absence of significant contamination

Sterilization

removing and destroying all microbial life

Commercial sterilization

killing Clostridium botulinum endospores from canned goods

Disinfection

destroying harmful microorganisms

Antisepsis

destroying harmful microorganisms from living tissue

Degerming

the mechanical removal of microbes from a limited area

Sanitization

lowering microbial counts on eating utensils to safe levels

Biocide (germicide)

treatments that kill microbes

Bacteriostasis

inhibiting, not killing, microbes

inhibition of cell wall synthesis

penicillin, cephalosporins, bacitracin, vancomycin

inhibition of protein synthesis

chloramphenicol, erythromycin, tetracyclines, streptomycin

inhibition of nucleic acid replication and transcription

quinolines, rifampin

injury to plasma membrane

polymyxin B

inhibition of metabolite synthesis

sulfanilamide, trimethoprim

effectiveness of treatment on microbial death depends on:

number of microbes, environment, time of exposure, microbial characteristics

what has a low temperature (bacteriostatic) effect on microbes?

deep-freezing, refrigeration, lysophilization

osmotic pressure

uses high concentration of salts and sugars to create a HYPERTONIC environment to cause plasmolysis

autoclave

heat and pressure create sterilization, cannot kill endospores

what are the main classes of microbial drugs?

antibiotic, antifungal, antiviral, antiprotozoan, antihelminthic

Selective toxicity

selectively finding and destroying pathogens without damaging the host

Chemotherapy

use of chemicals to treat disease

Antibiotic

a substance produced by a microbe that, in small amounts, inhibits another microbe

Antimicrobial drugs

synthetic substances that interfere with the growth of microbes

Narrow spectrum of microbial activity

drugs that affect a narrow range of microbial types

Broad spectrum antibiotics

affect a broad range of gram-positive or gram-negative bacteria

Superinfection

overgrowth of normal microbiota that is resistant to antibiotics

bactericidal

kills microbes directly

persister cells

microbes with genetic characteristics allowing for their survival when exposed to an antibiotic

Sugerbugs

bacteria that are resistant to large numbers of antibiotics

what are chemical elements for microbial growth?

carbon, nitrogen, and some sugar

how does resistance develop?

application and overuse of antibiotics

central dogma

DNA -- mRNA -- Protein -- Function

DNA replication

process in which genome’s DNA is copied within its cells, DNA makes a copy of itself

translation

creates proteins from RNA -- euk: cytoplasm // prok: cytoplasm

transcription

generates RNA from DNA -- euk: nucleus // prok: cytoplasm

RNA processing

sequence of events through which primary transcript from a gene acquires its mature form

genetic code

set of rules that determines how a nucleotide sequence is converted to an amino acid sequence of a protein

codons

groups of three mRNA nucleotides that code for a particular amino acid

Fungal thallus (body)

consists of hyphae filaments; mass of hyphae is a mycelium

Septate hyphae

contain cross-walls

Coenocytic hyphae

do not contain septa

yeast characteristics

nonfilamentous and unicellular
budding yeasts divide unevenly
fission yeasts divide evenly

Dimorphic fungi

yeastlike at 37c and moldlike at 25c

what are the medically important fungi?

Zygomycota, Microsporidia, Ascomycota, Basidiomycota

mycosis

fungal infection

systemic mycoses

deep within body

subcutaneous mycoses

deep within body

subcutaneous mycoses

beneath the skin

cutaneous mycoses

affect hair, skin, and nails

superficial mycoses

localized (ex. hair shafts)

Opportunistic mycoses

fungi harmless in normal habitat but pathogenic in compromised host

Entamoeba histolytica

causes amebic dynsentery

Acanthamoeba

infects corneas and causes blindness
Balamuthia: granulomatous amebic encephalitis

Toxoplasma gondii

transmitted by cats; causes fetal infections

Cryptosporidium

transmitted via feces; causes waterborne illness

Plasmodium

casues malaria

Symptoms

changes in body function that are felt by a patient as a result of disease

Signs

changes in a body that can be measured or observed as a result of disease