Lecture 16 - Culturing and Counting Bacteria

Defined Media

All component and their ratios are known

Complex Media

All components and their ratios are unknown

Agar is a complex

polysaccharide

Agar is used as…

solidifying agent for culture media in petri plates, slants, and deeps

Agar is generally not…

metabolized by microbes

Agar liquefies at…

100°C

Agar solidifies at…

~40°C

Selective Media

encourages the growth of certain organisms and discourage others

Differential Media

enable different species to be distinguished from each other

Enrichment media

encourage the growth of a specific organism

Selective medium will have a…

growth-inhibiting additive, such as bile salts, crystal violet or an antibiotic, which will limit growth on the medium to only those organisms that are desired

Mannitol Salt Agar (MSA)

High concentrations of salt contains mannitol and phenol red

MacConkey Agar

Crystal violet, neutral red and Bile salts and lactose

Differential medium - Blood agar

Allows for differentiation of a particular chemical reaction yield an observable characteristic associated with the growth a particular organism o group of organisms that are able to grow on the medium

β-hemolysis

• Complete lysis, resulting in a clear zone around the colony

• E.g. Streptococcus pyogenes

α-hemolysis

• Partialysis, resulting in greenish coloration around the colony

• E.g. Streptococcus pneumoniae

γ-hemolysis

• no lysis, no color change

• E.g. Enterococcus facecalis (formerly called group D Strep)

Deep freezing temps

-50 to -95°C

Lyophilization (freeze-drying)

Frozen (-54 to -72 °C) and dehydrated in a vacuum

What are the two main types of microbiota?

• Permanent

• Transient

What are the locations of commensal/mutualistic Microorganisms?

• Skin

• Oral Cavity

• Upper respiratory tract

• Intestines

• Urogenital tract

Areas and fluids of the body once thought to be “sterile” have been found to…

contain microbial DNA

What are the ways to classify microbes?

• Shape

• Staining pattern

• Biochemical

• Physiological differences

• Genome sequencing

Traits for bacterial classification

• Comparison of 16S rRNA structure and sequences

• Whole genome sequencing data

• Metabolic traits

• Ecological traits

Phylum Crenarchaeota are mainly…

hyperthermophiles

Phylum Crenarchaeota - Genus Sulfolobus

Aerobic and anaerobic enviornments

Phylum Crenarchaeota - Genus Thermoproteus

Strictly anaerobic

Phylum Eurarchaeota

• Classes Methanobacteria, Methanococci, Methanomicrobia

  • Called methanogens

• Classes Halobacteria (halophiles)

Euryarchaeota - Key Characteristics

Includes methanogens and extreme halophiles

Euryarchaeota - Common Habitat

Swamps, gut of ruminants, salt lakes

Euryarchaeota - Example

Methanobacterium

Crenarchaeota - Key Characteristics

Mostly extreme thermophiles; sulfur metabolism

Crenarchaeota - Common Habitat

Hot springs, hydrothermal vents

Crenarchaeota - Example

Sulfolobus

Thaumarchaeota - Key Characteristics

Ammonia-oxidizing; important in nitrogen cycle

Thaumarchaeota - Common Habitat

Soils, oceans

Thaumarchaeota - Example

Nitrosopumilus

Korarchaeota - Key Characteristics

Rare, thermophilic; known mainly by moleculsr studies

Korarchaeota - Common Habitat

Hot enviornments

Korarchaeota - Example

Korarchaeum

Nanoarchaeota - Key Characteristic

Very small; symbiotic/parasitic lifestyle

Nanoarchaeota - Common Habitat

Hydrothermal vents

Nanoarchaeota - Example

Nanoarchaeum equitans

Alpha-Proteobacteria : Key Features

Often symbiotic or intracellular pathogens and some are nitrogen-fixing

Alpha-Proteobacteria : Representative Genera/Examples

Rhizobium, Rickettsia, Caulobacter

Alpha-Proteobacteria : Medical or Ecological Importance

Nitrogen fixation in plants, typhus, rickettsial diseases

Beta-Proteobacteria : Key Features

Many are chemolithotrophs or human pathogens

Beta-Proteobacteria : Representative Genera/Examples

Neisseria, Nitrosomonas, Bordetella

Beta-Proteobacteria : Medical or Ecological Importance

Gonorrhea, meningitis, pertussis

Gamma-Proteobacteria: Key Features

Facultative anaerobes, many are enteric or aquatic pathogens

Gamma-Proteobacteria: Representative Genera/Examples

Escherichia, Salmonella, Vibrio, Pseudomonas

Gamma-Proteobacteria: Medical or Ecological Importance

Food poisoning, cholera, urinary tract infections

Delta-Proteobacteria: Key Features

Mostly predatory or sulfur-reducing bacteria and some form fruiting bodies

Delta-Proteobacteria: Representative Genera/Examples

Myxococcus, Bdellovibrio, Desulfuovibrio

Delta-Proteobacteria: Medical or Ecological Importance

Soil ecology, bioremediation, predatory bacteria

Epsilon-Proteobacteria: Key Features

Often microaerophilic, slender, motile

Epsilon-Proteobacteria: Representative Genera/Examples

Helicobacter, Campylobacter

Epsilon-Proteobacteria: Medical or Ecological Importance

Gastric ulcers, gastroenteritis

Alphaproteobacteria

• Many of the bacteria are obligate or facultative intracellular bacteria

• Rickettsias, obligate intracellular pathogens, that require part of their life cycle to occur inside other cells called host cells

• R. rickettsii causes Rocky Mountain spotted fever

• Ehrlichia, Obligatory intracellular bactera, cause ehrlichiosis (destruction of white blood cells and inflammation)

Betaproteobacteria - Burkholderia (Genus)

aerobic, motile, single polar flagellum

Betaproteobacteria - Bordetella (Genus)

Fastidious, aerobic, non motile, aerobic, chemoheterotrophic; rods

Betaproteobacteria - Neisseria (Genus)

Fastidious, diplococci, aerobic, non-motile

Gammaproteobacteria - Legionellales (Order)

• Legionella (Genus): rod or coccoid shape, motile, aerobic

• Coxiella (Genus): produces spore like bodies

Gammaproteobacteria - Vibrionales (Order)

Vibrio (Genus) - faculatative anaerobic slightly curved rods

Gammaproteobacteria - Pasteurellales (Order)

• Pasteurella (Genus) - non-motile, pleomorphic

• Haemophiluis (Genus) - non-motile, pleomorphic

Gammaproteobacteria - Pseudomonadales (Order)

• Pseudomonas (Genus) - Metabolically diverse, Polar flagella. Single or tuffs, aerobic

• Moraxella (Genus) - aerobic, coccobacilus

• Acinetobacter (Genus) - occurs in pairs, aerobic, motile

Gammaproteobacteria - Enterpbacteriales (Order)

Faculative anaerobic gram-rods and when motile, they have peritrichous flagella

Enterobacteriaceae - Frank pathogen (Fp)

• Escherichia

• Salmonella

• Shigella

• Klebsiella

Enterobacteriaceae - Opportunistic pathogen (op)

• Enterobacter

• Proteus

Enterobacteriaceae - Plant pathogen (Pp)

Erwinia