Bacti 1

• Bacteria cells


  • Size: about 1 micron, ranges 0.3 - 10 microns
  • Prokaryotic cells
  • Material transport via diffusion
  • No tissue differentiation
  • Relatively simple genetic control
  • Reproduction via binary fission
  • Flagella for movement
  • Spend most of time starving
• Bacterial shapes

  • Coccus
  • Bacilli
  • Twisted rods and more
• Bacteria can exist individually but typically exists in colonies
• Bacteria create biofilms when clinging to surfaces
• Bacteria may be spore formers, but have a simple structure
• Bacterial cell walls

  • Many bacteria have cell walls
  • Cell walls are key targets for antibiotics
• Bacterial ribosomes


  70S ribosomes, functionally same as 80S in eukaryotes but structurally different
• 16S rRNA sequencing for taxonomy


  1. Recognizes bacteria identity

  2. Can identify bacteria history
• Prototrophic

  Bacteria can make their own nutrients from simple carbon and nitrogen sources
• Auxotrophic

  Bacteria can produce almost all their own nutrients except one or two essential sources
• Bacterial growth and multiplication

  Bacteria grow and divide until cells pile up into a colony
• Bacterial respiration types

  • Anaerobic respiration: other oxygenated molecules as terminal electron acceptor
  • Aerobic respiration: oxygen as terminal electron acceptor
  • Obligate anaerobes: find oxygen toxic
  • Facultative anaerobes: can live with or without oxygen
• Bacteria can produce tetrahydrofolate and two steps can be inhibited by antibiotics (Bactrim)
• Bacterial oxygen requirements

  • Aerobes: require oxygen
  • Microaerophiles: reduced oxygen concentrations
  • Capnophiles: prefer low oxygen and high CO2
  • Facultative anaerobes: can grow with or without oxygen
  • Aerotolerant anaerobes: don't like oxygen but can tolerate it
  • Obligate anaerobes: cannot survive in presence of oxygen
• GC content in bacterial chromosomes has different characteristics compared to the rest of the genome, contains pathogenicity genome and pathogenicity islands
• Methods of antibiotic resistance

  • Transformation: takes DNA from environment
  • Transduction: virus attacks bacterial cell
  • Conjugation: bacterial cell fusion allowing DNA transfer
  • Transposons: genetic elements that can copy and insert resistance genes
  • Integrons: genetic elements that often carry resistance genes and recombinase enzyme
• Quorum sensing


  Regulation of gene expression in response to fluctuations in cell-population density
• Bacteria produce and export an autoinducer protein (N-acyl homoserine lactone) which induces growth when concentration is high enough
• Restriction endonucleases cut DNA at specific palindromic sequences, bacteria avoid cutting their own DNA by methylation
• Bacterial genetics

  • Circular chromosomes, supercoiled in histone-like proteins
  • Replication not a circular process, can happen even if previous round unfinished
  • Both DNA strands have genes
  • CRISPR system detects and removes foreign DNA
• Bacterial gene terminology

  • Promotor: where RNA polymerase binds
  • Repressor: binding proteins that regulate gene expression
  • Operator: location where repressor binds
  • Activator: promotes gene transcription
  • Terminator: sequence that stops transcription
  • Operon: replication process system as a whole unit
• Bacterial growth is exponential
• CRISPR → Clustered Regularly Interspaced Short Palindromic Repeats

  • Used to detect foreign DNA (macrophage) and remove it (considered the bacterial immune system)
• • Integrons- genetic element that often carries a resistance gene and a recombinase enzyme
  • Often found on plasmids and inserts via homologous recombination
• • Transposons- genetic elements that can copy themselves and insert in a different chromosomal location, typically contains resistance genes
  • If inserted into a transferable plasmid, a new host can quickly become resistant.
• Conjugation- One bacterial cell fuses with another, allowing DNA to travel from one to another. DNA being transferred carry anti-biotic and virulence genes.

  
  

  Very likely that this is the method that passes antibiotic resistance.
• Transduction- Virus infects bacteria, picks up some of its DNA, then goes onto infect other cells. The virus may pick up antibiotic or virulence factors.

  
  

  Very unlikely that this is the method that passes antibiotic resistance.
• Transformation- Takes DNA from environment, typically small bits and portions but can occasionally take larger DNA genomes/genes