Microbio Exam 1 Week 2

Cocci

usually round

divide to reproduce

Diplococci

remain in pairs after dividing

Streptococci

divide and remain attached in chainlike patterns

Staphylococci

divide in multiple planes and forms grape like clusters

Monomorphic

keep one shape

Pleomorphic

change shape

ex: rhizobium

Surface-to-Volume Ratios, Growth Rates

free-living smaller cells tend to grow faster than free-living larger cells, and for a given amount of resources

higher surface to volume ratio = smaller cell

supports a faster rate of nutrient and waste exchange per unit of cell volume compared with larger cells

Wavelength

different types of EMR fall on an electromagnetic spectrum, defined by wavelength and frequency

ex: visible light

wavelength of light used is a major factor in resolution

shorter wavelength = greater resolution

Magnification

describes the capacity of a microscope to enlarge an image

objective and clear

Resolution

the ability to distinguish two adjacent objects as distinct and separate

wavelength of light used

numerical aperture: light gathering ability of the objective lens

limit for light microscope is 0.2 um

objects closer than 0.2 um cannot be resolved as distinct and separate

Refraction

when light rays pass through the two materials (specimen and medium aka stain), rays change direction from a straight path by bending or changing angle at the boundary between the materials

Refractive Index

a measure of the light bending ability of a medium

must be changed from what their mediums is to obtain contrast

Creating Resolution

1. contrast between object and its surroundings

2. wavelength smaller than object

3. detector with sufficient resolution for given wavelength

Oil Immersion

oil has same refractive index as glass

increases the maximum angle at which light leaving the specimen can strike the lens

if using a microscope on 100x

Darkfield Microscopy

opaque disk blocks most of the light from illuminator

only light that reaches the objective = refracted or reflected from the specimen

bright objects on a dark screen

Phase Contrast

one set of light rays comes directly from the light source, other comes from reflected or diffracted light from specimen

structures that differ in refractive index will differ in levels of darkness

Fluorescence Microscope

produces images by exciting a specimen with wavelength of light that triggers object to emit fluorescent light

microbe is stained by fluorochromes that absorb light and emit visible fluorescent light

Electron Microscopy

uses an electron beam to create an image with electromagnets acting as lenses

limited resolution bc it uses natural light

generate images at resolution levels of up to 1000-fold greater than possible for light microscopy

used to observe sub-cellular structures/organelles and viruses

two types: transmission electron microscope and scanning electron microscope

Transmission Electron Microscope

visualizes small things like tissue structures or sub-cellular structures

Scanning Electron Microscope

observes the surfaces of cells

Wet Mount

drop of liquid placed on a slide

Smear

dried preparation of bacterial cells on a glass slide - evenly distributed thin layer

Heat Fixation

smear is fixed (attached) on the slide by heat otherwise smear will wash away by stain

coagulates bacterial proteins so bacteria stick to the slide surface

Staining

coloring microbes with a dye that creates contrast between the bacteria and the background, and emphasizes certain microbial structures

enables the study of microbial properties and to group the microbes in groups for diagnosis

postive vs negative stain

Bacterial Staining

solutions consisting of a solvent (usually water or ethanol) and a colored molecule (often benzene), the chromogen

Simple Stains

use a single dye

don’t distinguish organisms and structures

by differing staining reactions

Differential Stains

use two or more dyes that react differently with various kinds or parts of bacteria, distinguishing them

Gram Stain

developed by Hans Christian Gram

differential stain

shows differences in cell wall structures, thick vs thin

Gram Positive

remain purple stained

has a thick cell wall, so the CV-I remains in the cell

don’t have an outer membrane

Gram Negative

turns red stained

has a thin cell wall, so alcohol destroys the layer and the CV-I leaves the cell

have an outer membrane

Acid-Fast Stain

are gram positive

have a waxy mycolic acid constituent of their cell walls

detects the presence of cells walls rich in mycolic acid

uses carbol fushin to stain everything and acid alcohol as a decolorization agent, methylene blue counterstain

Endospore Stain

detect the presence of an endospore in a cell, which arise from undesirable environmental conditions

Bacterial Spores

uses heat to push primary stain malachite green into endospore

washing with water decolorizes the cell, but endospore retains green stain

cell is then counterstained with pink safranin

Spontaneous Generation Myths

maggots from rotting meat

fleas from hair

flies from fresh and rotting fruit

mosquitoes from stagnant pond water

termites are generated from rotting wood

Francescos Redi’s Experiment

maggots could only form when flies were allowed to lay eggs in meat

maggots were offspring from flies, not the product of spontaneous generation

John Needham

briefly boiled broth infused with plant or animal matter hoping to kill preexisting microbes, he then sealed the flasks

argued that new microbes must have arisen spontaneously

he likely didn’t boil the broth enough to kill preexisting microbes, which is why some continued to grow

Lazzaro Spallanzani

heated but sealed flasks remained clear

suggested microbes were introduced into these flasks from the air

needham argued that life originates from a life force that was destroyed during the longer boiling

Louis Pasteur: Disproving Spontaneous Generation

created flasks with long curved necks

“swan-neck flask” experiments

boiled the solutions and then left them exposed to air

results: no growth of microorganisms in swan neck flasks

demonstrated that microbes are present in non-living matter - air, liquids, and soilds

Germ Theory of Disease

diseases may result from microbial infection

Ignaz Semmelweis and Joseph Lister

Ignaz Semmelweis

proposed that physicians were somehow transferring the causative agent to their patients

importance of handwashing to prevent transfer of disease

Joseph Lister

began using carbolic acid (phenol) spray disinfectant during surgery

extremely successful efforts in reducing post surgical infection

Robert Koch

proposed a series of postulates based on the idea that the cause of a specific disease could be caused by a certain microbe

able to identify the causative agents of certain diseases = one disease one microbe

limitations: ethical concerns with his experiment which involved injecting mice with diseases and some microbes can cause multiple diseases

Vaccination Creation

coined by Edward Jenner

observed that milkmaids who got cowpox were immune to smallpox

this led him to developing a vaccine for smallpox using cowpox microbes

Louis Pastur: made the rabies vaccine

Variolation

injecting infected postules into a healthy individual to provide immunity

early vaccine

First Antimicrobial Drugs

antiseptics were first created but couldn’t be taken internally

researchers (Paul Ehrlich) wanted a “magic bullet”, or antibiotic that would only kill microbes and not harm the host

Development of Antibiotics

Alexander Fleming made mold containment which caused a “zone of clearing” with no mold

penicillin was created

modern times sees the overuse of these antibiotics causing multi-drug resistance pathogens

The Endosymbiotic Theory

argued that eukaryotic organelles like mitochondria and chloroplasts are of prokaryotic origin

evidence:

1. mitochondria and chloroplasts resemble bacteria in size and shape

2. contain nuclear DNA, like prokaryotes

3. can reproduce independently of host

4. ribosomes resemble prokaryotes, and protein synthesis mechanism is similar to bacterias

5. antibiotics that inhibit protein synthesis on ribosomes in bacteria also prevents it on mitochondria and chloroplasts

Bacterial Cell - Cell Envelope

cytoplasm of bacterial cells is a gel like network of proteins and other molecules, contained by cell membrane

outside of membrane, the cell body is enclosed by the cell wall

outside cell wall, gram negative bacteria have outer membrane

cell membrane, cell wall, and outer membrane (for gram negative) constitute the cell envelope

chromosome is organized within cytoplasm as a system of looped coils called the nucleoid

Plasma Membrane

fluid mosaic model, a dynamic moving model

cell (plasma) membrane separates the cytoplasm from the outside environment

phospholipid bilayer with proteins

Bacterial Membrane Proteins

peripheral (interact with membrane indirectly) and integral (attached to membrane) transmembrane proteins

support for structures that protrude from the cell (flagella and pili)

transport of substances in and out of the cell across the membrane

signaling and communication, ex: legumes and nitrogen fixing

exhibits selective permeability, allowing some things to enter and others to not

Passive Transport

moves nutrients with the concentration gradient, no energy needed

Active Transport

moves nutrients against the concentration gradient, energy needed

Coupled Transport

the use of energy from one gradient to drive transport up another gradient

Symport

two molecules moving in the same direction, active transport

ex: lactate and H+

Antiport

two molecules moving in opposite directions, active transport

Simple Diffusion

passive transport

no energy needed, goes from high to low concentration

Facilitated Transport

passive transport, no energy needed (high to low)

uses a transporter to move something through a channel

water channel = aquapore

Active Transport

molecules in a cell are kept at different concentrations between the membrane

ex: symport, antiport, group translocation, ABC transporters

Group Translocation

active transport

happens only in prokaryotes

transport of sugars, modified in the process

Peripheral Protein

interact with the membrane indirectly

Transmembrane Protein

interact with the membrane directly, spans the entirety of the cell membrane

ABC Systems

active transport

uses energy from ATP hydrolysis to transport molecules in low concentrations

can expel wastes, antibodies, efflux transporters, and have multidrug resistance