Biology: Chapter 27- Bacteria and Archea

3 Domains of life

Bacteria, Archea, and Eukarya

Why is the phylogenetic tree more like a “shrub” than a “tree”?

Early life evolved through horizontal gene transfer(HGT)

Ways that Archea are similar to Eukarya

DNA replication, transcription, and translation processes.

Presence of histones

Similar RNA polymerases

Eukarya have many introns and Archea have some

Ways that Archea are similar to Bacteria

Prokaryotic cell structure

Binary fission reproduction

Small size

No nuclear envelope or membrane-enclosed organelles

Archea have some introns and Bacteria have almost none

External structures of bacterial cell

Capsule – Protects against desiccation, immune defense evasion

Cell Wall – Provides shape, protection (peptidoglycan in bacteria)

Plasma Membrane – Regulates material exchange

Flagella – Movement

Pili/Fimbriae – Attachment to surfaces, DNA transfer (sex pili)

Internal structures of bacteria cell

Nucleoid – Contains bacterial DNA

Plasmids – Small, circular DNA for genetic exchange

Ribosomes – Protein synthesis

Cytoplasm – Contains enzymes and molecules for metabolism

Bacteria shapes

Bacillus (Rod-shaped)

Coccus (Spherical)

Spirillum (Spiral-shaped)

Arrangements of bacteria

Strepto- (Chains): Streptococcus

Staphylo- (Clusters): Staphylococcus

Gram-positive bacteria

P(positive)urple- Thick layer of peptidoglycan with no outer membrane, and low lipid content(no bi-layer).

Retains crystal violet because of its thick peptidoglycan

Gram-negative bacteria

PiN(negative)k- thin layer of peptidoglycan with the outer membrane and has a lipid bilayer.

Retains only pink in its cell membrane

Positive taxis

Movement towards stimulus.

Ex- Positive chemotaxis/phototaxis- Move toward nutrients like glucose/ light

Magnetotaxis

Negative taxis

Movement away from stimulus.

Ex- Negative chemotaxis/ phototaxis- Move away from chemicals or toxins/ light

Magnetotaxis

Binary fission

Asexual reproduction- one cell divides into two

Conjugation

Transfer of DNA via a pilus

F+ (donor)

F- (recipient)

Transformation

Uptake of free DNA from the environment where the cell takes in plasmid and copies info into the cell

Transduction

Transfer of DNA via a bacteriophage(virus)

Antibiotic resistance and natural selection

Antibiotics kill suseptable bacteria but those who are mutated could be resistant. Those resistant bacteria will survive in the process of natural selection and will pass that resistance to their offspring. Consistant use of antibiotics will cause quicker resistance.

EX- MRSA( methicillin-resistant staphylococcus aureus)

Photoautotrophs

Photo-gets energy from light, Autotroph- inorganic carbon source (CO2)

Ex- Cyanobacteria, plants

Chemoautotroph

Chemo- gets energy from inorganic materials, Autotroph- inorganic carbon source (CO2)

Ex- Nitrifying bacteria (in soil)

Photoheterotroph

Photo- gets energy from light, Heterotroph- gets carbon from organic materials

Chemoheterotroph

Chemo- gets energy from organic materials, Heterotroph- gets carbon from organic materials (eating)

Ex- Humans, E-coli

Obligate Aerobes

Require oxygen

Obligate Anaerobes

Killed by oxygen

Facultative anaerobes

Use oxygen but can survive without it

Aerotolerant Anaerobes

Tolerate oxygen but don’t use it

Microaerophiles

Require low oxygen

Nitrogen fixation

N2(atmospheric oxygen)→ NH3

Rhizobium in root nodules for better soil quality

Ammonification

Organic nitrogen→ NH4+

Nitrification

NH4+→NO2- →NO3-

Furthers process of nitrogen fixation to make nitrogen more available to plants

Assimilation

NO3- (Used by plants)

The uptake of NO3- to convert it into NH4+. Essential for building proteins and amino acids.

Denitrification

NO3- → N2 (return to the atmosphere)

Biofilm

A community of bacteria embedded in a self-produced matrix.

Ex- Dental plaque

Microbiome

The collection of microbes living on/in an organism.

Ex- Gut microbiome

Thermophile

Extremophile- High heat

Ex- Hydrothermal vents

Halophile

Extremophile- High salt

Ex- Dead sea

Acidophile

Extremophile- Low pH

Ex- Volcanic pools

Alkaliphile

Extremophile- High pH

Psychrophile

Extremophile- Cold environments

Endotoxin

Pathogen- Releases toxins when they die. In lipid-bilayer.

Ex-General inflammation and fever

Exotoxin

Pathogen- Releases toxins while they are alive. In proteins.

Ex- Targeted effects (neurotoxins)

Uses for bacteria in research

Antibiotic production, Fermentation, Bioremediation (oil spill cleanup), and medical research.