Microbiology Exam #1 (msu brandy roberts)

microbiology

study of microbes

microbes

forms of life too small to be seen with the naked eye. (bacteria, fungi, algae, protozoa)

how microbes interact with humans, with food and how they can be used in humans (among other aspects)

what does the field of microbiology examine?

metabolism, growth, reproduction, genetic variation/evolution, adaptation/response to environment, homeostasis

basis for life?

polypeptides, nucleic acids, lipids, polysaccharides

macromolecules for life?

polypeptides

serve many purposes; one of the most important is the function of enzymes as catalysts of chemical reactions

polysaccharides and polypeptides

can be embedded in a lipid bilayer, forming a cell's plasma membrane. this separates external environment from interior of cell

nucleic acids

dna/rna; critical storehouses of genetic information; comparisons of DNA sequences are how we can break life into three large groups known as domains

dna sequencing

used to compare sequences of ribosomal RNA genes in different organisms in the 1970s

bacteria, archaea, eurkarya

3 domains

viruses

aren't considered alive; don't replicate outside host cell; have little to no biochemical activity outside host cell; inert/nonreactive outside host cell; can't be seen with naked eye

fast, cheap, easy to grow; produce enzymes and other molecules for industrial/medical uses; have small numbers of genes, making them simpler to study; genetic manipulation of single-celled bacteria is usually much easier than multicellular eukarya.

why study microbes?

ribozymes

rna molecules that have ability to catalyze reactions

dsDNA provides backup copy of genetic info in case of problem; dna is more stable than rna

why does bacteria today use double stranded dna instead of single stranded rna?

examining effects of single mutations in dna individually; studying and comparing pieces of genomes to each other (bioinformatics) across domains

2 different perspectives to examine microbial genomes

yes; altering genomes of microbes can mass produce the molecules humans want

can studying genetics of microbes help us to use them to benefit humans?

heterotroph

ingest preformed organic molecules

autotroph

produce organic molecules

fermentation

doesn't need oxygen but doesn't yield much energy for microbes

aerobic respiration

requires oxygen but yields much more energy

Microbes in the intestines

Plaque on teeth

Slime on rocks on beaches

Mold growths on bathroom surfaces

microbes live in diverse groups in nature with many different members forming a microbial community and ecosystem such as:

wasn't always believed that microbes caused disease

people believed disease was caused by angry gods or bad air

people thought microbes could spontaneously form

how are microbes associated with disease?

louis pasteur and robert koch

who debunked the ideas of spontaneous generation and what caused disease?

louis pasteur

performed a simple yet elegant experiment to disprove spontaneous generation theory in the late 1800s (broth)

robert koch

determined Bacillus anthracis and Mycobacterium tuberculosis were the causes of anthrax and tuberculosis (respectively).

His work with anthrax helped sheepherders and cattle ranchers avoid costly animal losses

koch's postulates

made it possible for others to determine which microbes caused which diseases.

plague

microbial disease that had profound impact on humanity

Prevention of infection:

Use of antiseptics (Joseph Lister)

Sanitation improvements (sewage treatment)

Food/water safety (pasteurization)

Personal hygiene improvements

Vaccination

Treatment of infections (antibiotics!)

reduction of deaths?

spherical, rod-shaped, comma-shaped, spiral, pleiomorphic (varied)

shapes of bacteria?

hyphae, mycelia, trichomes

bacterial multicellular organizations

hyphae

branching filaments of cells

mycelia

tufts of hyphae

trichomes

smooth, unbranched chains of cells

varies greatly

usually smaller than eukaryal cells

often 0.5-5 micrometers

bacteria size

nucleoid, chromosome-packaging proteins, enzymes involved in synthesis of dna/rna, regulatory factors, ribosomes, plasmids, enzymes involved in breaking down substrates, inclusion bodies, gas vesicles, magnetosomes, cytoskeletal structures

what is in the cytoplasm of bacterial cells?

nucleoid region, housing the chromosomes and dna replication machinery

largest area in cytoplasm of bacterial cells?

cytoskeleton

a series of internal proteins that assist in keeping everything in (or moving it to) the right locations in cells. some proteins involved in cell wall synthesis during cell divison

plasmids, magnetosomes

cytoskeletal proteins involved in moving internal items

plasma membrane

all cells have it; separates the interior of the cell from the external environment

Usually composed of a phospholipid bilayer with embedded proteins; may have sterol molecules called "hopanoids" in it to help with stability across temperature ranges

O2 and CO2 are small and can diffuse across readily;

H2O is helped across by aquaporin protein channels;

Osmosis can cause a cell to swell with water or shrivel as water leaves, but a strong cell wall can help keep a bacterial cell alive during these hardships.

How do items cross the PM and get into a cell?

osmosis

flow of water across the PM toward the side with a higher solute (particle) concentration.

facilitated diffusion and active transport

But how do nutrients cross the PM?

facilitated diffusion

using a protein channel to move particles with a concentration gradient (no energy)

active transport

using energy to move particles against a concentration gradient

plasma membrane

can also be used for capturing energy; can hold sensory systems; respiration/photosynthesis; derive energy for motion (flagella)

proton motive force

created by embedded electron transport chains

bacterial cell wall

crucial structure; composed of crosslinked strands of peptidoglycan subunits forming a matrix; gives cells their shape and protection from osmotic lysis/mechanical forces

peptidoglycan disaccharide subunit

N-acetylmuramic acid (NAM) with a small peptide chain and N-acetylglucosamine (NAG)

yes - naturally by lysozyme and lysostaphin secretions; Artificially by 𝛽-lactam antibiotics

Can the cell wall structure be degraded?

lysozyme

cleaves backbone of peptidoglycan

lysostaphin

acts on the crossbridge of certain staphylococcus species only

𝛽-lactam antibiotics

prevent peptidoglycan cross-linking, which weakens cell wall structure

antibiotic resistance

some bacteria can produce an enzyme to destroy critical 𝛽-lactam structure

add second drug to inhibit that enzyme and restore first drug's efficiency

stain method

1884, Hans Christian Gram; can separate many microbes into one of two classes

2 classes of microbes

gram positive and gram negative

gram-positive

thick outer layer of peptidoglycan

very narrow periplasmic space

teichoic acids in peptidoglycan (negative)

gram-negative

varying width periplasmic space containing very thin layer of peptidoglycan

outer membrane composed of lipospolysaccharide (LPS)

flagella

motility; spiral, hollow, rigid filaments extending from cell surface

filament, hook, basal body

3 basic parts of motility from flagella

filament

multiple flagellin proteins

hook

connects filament to basal body

basal body

disk-like structure that produces torque on filament to turn it like a propeller

chemoreceptor proteins

sense changes in concentrations of attactants or repellents

spirochetes

flagella in periplasm; as they spin they rotate entire cell body like a corkscrew

gliding motility

smooth sliding over a surface, not well understood

twitching motility

slow, jerky process using fibers (pili) that can be extended, attached to a surface, and pulled back to pull along a surface

capsules

thick layer of polysaccharides surrounding some cells; provide adhesion; defense against host immunity; protection against drying out (desiccation); help bacteria form biofilms

biofilms

provide protection and enhanced survivability in harsh environments

examples: dental plaque, mold on bathroom surfaces

surface arrays (s-layers)

crystalline array of interlocking proteins; found in gram-positive and gram-negative cells; armor

species

group of strains sharing common features while differing considerably from other strains

genus

group of closely related species

eukaryal cells

membrane bound nucleus

larger than bacterial/archaeal cells

organelles

may have cell wall

complex internal cytoskeleton

nucleus

storage and expression of information

double membrane structure

contains DNA

nucleolus

nucleolus

non membrane bound; exists within the nucleus (ribosome synthesis)

transcription

occurs in nucleus

translation

occurs in cytoplasm

mitochondria and chloroplasts

cell metabolism

electron transport chains to produce ATP

semiautonomous

most proteins originate from DNA in nucleus

mitochondria

later stages of cellular respiration

chloroplasts

use ATP they produce to fix carbon into organic compounds

semiautonomous

mitochondria and chloroplasts; each has own DNA, ribosomes, transcription machinery, and can replicate independently of the rest of the cell

plasma membrane

role in homeostasis; phospholipid bilayer with embedded proteins that allow molecule transport

homeostasis

ability to maintain an internal environment vs. changes outside

cell wall

role in cell support; can separate eukaryal cells into those with or without; vary widely among domains; cellulose and chitin; some only create at certain points in a cell's life cycle

cytoskeleton

role in cell structure; contributes to cell shape; can't provide same protection as cell wall; involved in intracellular tracking; motion and cell division; motion by cilia/flagella; can be exploited by pathogens

microtubules, microfilaments, intermediate filaments

three major structures of cytoskeletons

cell division

assisted by spindle fibers (cytoskeleton)

saccharomyces cerevisiae

fungi model organism; heterotrophic; chitin cell walls; used to make bread, beer, and wine; easy, cheap tool to study eukaryotic structures/gene expression

giardia lamblia

protozoa model organism; some heterotrophic, some photosynthetic; variable cell walls; different motility strategies; different reproduction strategies; genetically "old,"; lacks mitochondria; causes human disease

dictyostelium discoideum

slime mold model organism; model for studying ecology, cell motility, and cell-cell communication

physarum

slime mold model organism; fuses many cells into a continuous, multinucleate giant cell

chlamydomonas

algae model organism; two-flagella form good for studying eukaryal flagella biogenesis/function; also studied because of its ease of growth and durability.

algae

Some are single-celled, but many are multicellular; all are photosynthetic with cellulose cell walls; can produce great amounts of oxygen through photosynthesis in the oceans

protozoa

can cause significant human disease

fungi

less likely to cause disease but can do so in immunocompromised individuals

protozoa and fungi

can cause significant disease in plants

primary producers (energy) or biodegraders (recycling)

beneficial roles of eukaryal microbes

archaeons

look like bacteria but genetic analyses show them to be different; live in some of the inhospitable places (for humans) on earth

methanogens

poorly characterized group of microbes capable of producing methane as a byproduct; energy released can be used to fix carbon; strict anaerobes; found in human gut and swamp sediments; possess a great deal of diversity but share a common metabolic property

archaeon structure

0.5-5 micrometers in diameter; similar shapes to bacteria/eukarya; singular, circular chromosomes; lack nucleus; dna is complexed with histones; pm is unique

morphology of archaea

generally 0.5-5 micrometers; can vary