Download Microbes in the Environment

Objectives
• Use appropriate microbiology media, test
systems, and lab equipment.
• Describe the general properties and
characteristics of bacteria
– By doing this, students will be able to observe
growth characteristics of bacteria
Microbes in the Environment
Ubiquity of Microorganisms
• This means that microorganisms can be found
everywhere
– Soil, water, plants, animals
• Many microbes are free-living
– They don’t live on a specific host
– Most are nonpathogenic (non-disease causing)
• Today we will culture microbes from the
environment
Ubiquity of Microorganisms
Simple streak pattern
Culturing Microbes
• Microbes need certain nutrients and growth
factors to grow and reproduce
– Carbon
– Nitrogen
– Sulfur
– Phosphorus
– Trace elements
– Organic growth factors
Culture Media
• Culture medium: Nutrients prepared for
microbial growth
• Sterile: No living microbes
– Autoclave at 121°C for 15 min at 15 psi
– Steam under pressure
• Inoculum: Introduction of microbes into
medium
• Culture: Microbes growing in/on culture
medium
Culture Media
• A. Chemically defined media: Exact chemical
composition is known
• B. Complex media: Extracts and digests of
yeasts, meat, or plants
– Chemical composition varies slightly from batch to
batch
– Nutrient broth
Agar
• Complex polysaccharide derived from
seaweed
• Used as solidifying agent for culture media in
Petri plates, slants, and deeps
• Generally not metabolized by microbes
• Liquefies at 100°C
• Solidifies at ~40°C
– Once solid, it will remain until heated again to
100°C
Labeling/Incubating Plates
• Initials
• Date
• Sample
Labeling/Incubating Plates
Labeling Plate
• On back of plate with
sharpie
• Initials
• Date
• Sample
Incubation Plate
• 37⁰C
• Upside-down
• 24-48 hrs
What to Expect
• Bacterial make colonies
– Thousands same cells
– All cells in colony originate from single parent
• Variety of shapes, sizes, and color of various
colonies