Bacterial Internal Structure

• This chemical “pool” (cytoplasm) is a prominent site for many of the

  cell’s biochemical and synthetic activities (functions for

  cell growth, metabolism, and replication are carried out)
• The cytoplasm also holds larger,

  discrete bodies such as the chromosome, ribosomes, granules, and actin strands
• Cytoplasm's major component is water (70%–80%), which serves as asolvent for a complex mixture of nutrients including sugars, amino acids, and other organic molecules and salts
• ribosome is a combination of a special type of RNA called

  ribosomal RNA, or rRNA (about 60%), and protein (40%).
• One method of characterizing ribosomes is by S, or Svedberg, 4units, which rate the molecular sizes of various cell parts that have been spun down and separated by molecular weight and shape in a centrifuge.
• Bacterial ribosomes are composed primarily of ribosomal

  RNA (rRNA) molecules
• Messenger RNA - Carrying genetic instructions
• Transfer RNA - Delivering amino acids
• Ribosomal RNA - Forming the ribosomal structure
• Ribosomal Proteins - Enabling protein synthesis
• Initiation - The replication of the nucleoid begins at a specific origin of replication, where the DNA is unwound and the two strands are separated.
• Elongation - DNA polymerase enzymes then replicate the DNA, synthesizing new complementary strands to create two identical copies of the genetic material.
• Segregation - The replicated nucleoids are then separated and distributed to the two daughter cells during cell division, ensuring each cell inherits a complete copy of the genome.
• Transcription - RNA polymerase

  enzymes use the DNA in the nucleoid as a

  template to synthesize messenger RNA (mRNA),

  which carries the genetic information to the ribosomes.
• Translation - Ribosomes located within the nucleoid use the mRNA as a blueprint to synthesize proteins, the

  functional molecules that carry out the instructions encoded in the DNA.
• The nucleoid is an irregularly shaped region that contains

  the cell’s chromosome and numerous proteins
• The chromosomes of most bacteria are a single circle of

  double stranded deoxyribonucleic acid (DNA), but some

  bacteria have a linear chromosome
• Bacterial chromosomes are longer than the length

  of the cell.
• E. coli's circular chromosome

  measures approximately 1,400 11m, or about 230-

  700 times longer than the cell
• Supercoiling is thought to be important. It produces a

  dense, central core of DNA with loops of DNA

  extending out from the core.
• Several nucleoid-associated proteins (NAPs) cause the

  chromosome to bend and fold, thereby also helping to

  pack the DNA into a smaller space.
• Plasmids are small, circular , double-stranded DNA

  molecules that exist independently of the main

  chromosome in bacteria and archaea.
• plasmids are typically much smaller than the host's genome and can replicate autonomously within the cell.
• Plasmids often carry genes that provide the host with

  specialized functions, such as antibiotic resistance or

  the ability to degrade complex compounds.
• Episomes – plasmids that are able to integrate into the

  chromosome and when integrated are replicated as part of the chromosome
• Plasmids are inherited stably during cell division, but they

  are not always equally apportioned into daughter cells and sometimes are lost
• Single-copy plasmids produce only one copy per host cell. Multicopy plasmids may be present at concentrations of 40 or more per cell.
• Plasmids Functions in Bacteria

  • Antibiotic Resistance
  • Degradation of Cmpounds
  • Virulence and Pathogenicity
  • Symbiotic Relatioships
• Plasmids play a crucial role in biotechnology, serving as

  versatile tools for genetic engineering and recombinant

  DNA technology
• Antibiotic Resistance

  Plasmids can carry genes that confer resistance to antibiotics, allowing bacteria to survive in the presence of these drugs.
• Degradation of Compounds

  Some plasmids encode enzymes that enable bacteria to break down and utilize complex organic compounds, expanding their metabolic capabilities.
• Virulence and Pathogenicity

  Plasmids can harbor genes that increase the ability of bacteria to infect and harm their hosts, contributing to their pathogenicity
• Symbiotic Relationships

  Plasmids in some archaea can facilitate the establishment of beneficial symbiotic relationships

  with other microorganisms, promoting survival and adaptation.
• Large subunit (50s)

  • made of 23s and 55s rRNA
• Small subunit (30s)

  • made of 16s rRNA
• storage inclusions - stores molecules, enclosed by single layer of proteins/phospholipids
• microcompartments (inclusions) - contain molecules + enzymes

  polyhedral shape, protein shell
• gas vacuole/ vesicles - store as; buoyancy - enclose in walls made of a single protein