Bacterial diversity

• what is taxonomy

  the science of classification
• what is taxonomy used for

  • identifies the relationships between groups of organisms
  • can be used to identify novel or previously unknown organisms
  • provides universal language of classification between scientists
• what is taxa

  categories of organisms

  reflects evolutionary or phylogenetic relationships 
• Carl Woese (1923 - 2012)

  • developed a first gene-based quantitative description of the tree of life
  • quantitative measure of relatedness
  • ribosomes and ribosomal RNA is present in all species
  • 16s rRNA is large enough and sufficiently diverse to get good quantitative data
• what are the important eukaryotic signature proteins

  • eukaryotic-like actin
  • many small GTPases
  • endosomal sorting complex required for transport (ECRT)
  • membrane deformation and phagocytosis-associated ESPs
  • ubiquitin
• what is gram negative bacteria called

  proteobacteria
• features of proteobacteria

  • metabolically diverse
  • many environmental habitats
  • symbionts
  • nitrogen-fixers
  • aquatic environments
  • major human pathogens exhibit chemotrophy (utilise glucose) under aerobic conditions
• rhizobiales - alpha

  • Agrobacterium - plant pathogen
  • Bradyrhizobium - symbiotic nitrogen fixer
  • Nitrobacter - nitrifying
  • Rhizobium - symbiotic nitrogen fixer
• neisseriales - beta

  • Neisseria - human pathogen
  • characterstic diplococci
  • N. meningitidis - meningitis - carried in 95% of population
  • N. gonorrhoeae - gonorrhoea
• Enterobacteriales - gamma

  largest sub-group of the proteobacteria, most pathogenic species of the group 

  • shigella
  • escherichia
  • salmonella
• shigella

  • human pathogen
  • Shigella dysenteriae
• escherichia

  • human commensal, some pathogens
  • common inhabitant of intestinal tract but uncommon pathogen
  • important research tool - E. coli
• salmonella

  • human pathogen
  • Salmonella enterica
• spirilla - delta

  • Bdellovibrio - uses other bacteria as a host
  • curved bacteria
  • potential antimicrobial
  • B. bacteriovorus - intracellular predator of gram negative bacteria
  • widespread in soils and aquatic environments
  • B. exovorus - an extracellular vampire like bacterial predator
• Campylobacterales - epsilon

  • Capylobacter 
  • Heliobacter 
• Capylobacter 

  • highly motile bacillus, curved
  • foodbome disease - C. jejuni
• Heliobacter 

  • has multiple flagella
  • cause of stomach ulcers
  • H. pylori
• how is gram-positive bacteria divided

  • firmicutes - low G+C
  • acintinobacteria - high G+C
• firmicutes

  • lactobacillales
  • lactobacillus
  • streptococcus
  • bacillales
  • staphylococcus
  • bacillus
  • clostridiales
  • clostridium
• lactobacillus

  • lactic acid producers, human commensal
  • variable size
  • rod shaped
  • used in fermented products (yoghurt/sauerkraut)
  • L. caseii - cheese
  • L. acidophilus - acid loving
• Streptococcus

  • many human pathogens and commencals
  • spherical/round
  • medically relevant
  • subdivided by haemolysis (oxidation of blood cells)
  • S. pyogenes (pus)
  • S. mutans (caries)
  • S. pneumoniae
• Staphylococcus

  • some human pathogens
  • spherical/round
  • S. aureus - boils, produces toxins
  • MRSA - major hospital acquired infection
  • S. epidermidis - commensal
• Bacillus

  • endospores, some human pathogen
  • rod shaped
  • endospore forming - enables survival during extremes of environment
  • B. anthracis - anthrax
  • B. cereus - contaminates cereals from soil
• Clostridium

  • anaerobes, endospores, human pathogens
  • rod shaped
  • forms endospores
  • location of spores helps identify species
  • C. tetani - spastic paralysis lockjaw
  • C. botulinum - flaccid paralysis
  • C. difficile - hospital associated diarrhoea
• actinobacteria

  • have a similar appearance to fungus when grown
  • Actinomycetales
• actinomycetales

  • Actinomyces
  • Frankia
  • Streptomyces
• Actinomyces

  • filamentous, branching, some human pathogens
  • faculative anaerobe
  • looks like fungal hyphae under microscope
  • important for soil ecology
• Frankia

  • symbiotic nitrogen fixers
  • filamentous
  • carry out nitrogen fixation in soil
  • atmospheric N to ammonia
• Streptomyces

  • filamentous, produce antibiotics
  • form mycelium
  • produce conidia - not the same as endospores
  • important producers of antibiotics
  • occurs during nutrient depletion therefore a survival mechanism for competition
  • aminoglycosides
  • tetracyclines
  • macrolides
  • amphotericin B
  • active against gram positive and negative bacteria and fungal infections