Week 6 Microbial Ecology and Controlling Microbial Growth

Week 6 Microbial Ecology and Controlling Microbial Growth New England Institute of Technology Dr. Shellee Morehead

Chapter 10 Episode 1 Microbial Ecology

Introduction • Microbial ecology- study of microbes and their interactions/relationships within the world

Symbiotic Relationships • Symbiosis- different species in the same environment living together • Neutralism- species have no effect on each other • Commensalism- beneficial to one species, no effect on the other (many indigenous microflora are commensals) • Mutualism- both species benefit • Parasitism-beneficial to one species, harmful to the other

Symbiosis • Gut flora 500 to 600 species living in our colon

Commensalism • Mites living on eyelashes, no effect on people

Mutualism • Lichen are fungus and algae or bacteria • Gut flora are also an example

Parasitism • Insert disease of choice here • Trypanasomas gambiense • African sleeping sickness

Indigenous Microflora • AKA normal flora • Bacteria, fungi, viruses, protozoa • 100 trillion cells make up our normal flora • Fetus usually has no indigenous microflora • Normal flora is very specific to its body site, due to p. H, temp (etc) requirements • Normally sterile: CSF, urine, blood

Transient Microflora • Due to constant exposure • Most vulnerable: warm, moist areas • Temporary due to epithelial shedding, bathing, unable to compete with normal flora

Normal Skin Flora • Mostly bacteria & fungi • Mostly anaerobes in deeper skin layers • Moist, warm hairy areas with oil & sweat glands have increased numbers • Dry areas have fewer • Most burn, wound & surgical infections are caused by transient microflora

Indigenous Microflora

Normal Flora of the Eyes & Ears • Middle & inner ear sterile • Outer ears & canal contain skin flora • May be transferred to middle ear with coughing, sneezing; may cause infections • Lysozymes in tears protects the eye

Respiratory Flora • Nose & throat have many microbes • Warm, moist • Mostly harmless; some are opportunistic • Some pathogenic; humans may be carriers • Usually lower respiratory tract has no microbes because of mucous membranes and defense mechanisms within the lungs

Oral Flora • Many aerobics & anaerobics • Food particles, sugars between teeth & within gums • A healthy human mouth includes G+ and G- bacteria; cocci, bacilli & spirilla; yeasts, molds, protozoa, viruses

www. dentistrytoday. com

GI Flora • Stomach p. H prevents growth of most indigenous & transient microflora • Helicobacter pylori (G- bacillus) may live in stomach; causes ulcers • Few microbes in duodenum, many in ileum & jejunum • Colon; greatest concentration of microbes in the body • Anaerobes (obligate, facultative, aerotolerant) • Many are opportunists (E coli)

E. coli

GU Microflora • Kidneys, ureters & bladder should be sterile • Distal urethra has many microbes • Usually don’t reach the bladder due to urination; may cause UTIs

Good & Bad Normal Flora • Microbial antagonism • Normal flora prevent the establishment of foreign (transient) microflora • Opportunistic pathogens • E. coli, Enterbacteriacae, Staph aureus • Biotherapeutic agents • Bacteria & yeasts which are taken in to re-establish microbial balance within the body

Biofilms • Microbes are usually (naturally) found in mixed groups • Secretions cause adherence = biofilm • Causes of endocarditis, cystic fibrosis, otitis media, renal calculi, periodontal disease • Causes of infections on indwelling medical equipment (urinary catheters, IV devices, endotracheal tubes); C, albicans, S. aureus, P. aeruginosa

Biofilms • Resistant to many antibiotics, disinfectants, inherent defense mechanisms • Members of a biofilm community strengthen the community as a whole; render it resistant to substances that are known to affect the individual species; prevent penetration into the biofilm by leukocytes

Biofilms http: //www. zmescience. com/science/what-arebiofilms/ http: //www. bayarealyme. org/blog/straight-talk-biofilms-new-answertreating-lyme-disease/

Dental Biofilm

Synergistic Infection • Polymicrobial infections; mixed infections • Often requires multiple antimicrobials to treat

Microbial Biotechnology • Production of therapeutic proteins • Humulin insulin, HGH • Production of DNA vaccines • Experimental; plasmids are being used to cause the production of antibodies • Vitamin production • Genetically engineered antibiotics • Bioremediation

Insulin production http: //slideplayer. com/slide/5784580/

Vitamin A http: //bioscriptionblog. com/2017/07/05/vita min-biofortification-nutrition/

Bioremediation in an Industrial Yard

Bioremediation in Manila http: //www. zmescience. com/ecology/bioreme diation-in-manila-philippines/

Quick Review • Define: symbiosis, mutualism, parasitism and commensalism • What are indigenous microflora? • Name 2 disease causing microorganisms • What is a biofilm?

Week 6 Episode 2 Chapter 8

Controlling Microbial Growth In Vitro BIO 122 Ch 8 New England Institute of Technology

Introduction • Encouraging growth of microbes • Discouraging growth of microbes

Factors Affecting Microbial Growth • Nutrients • Moisture • Temperature • p. H • Osmotic pressure • Barometric pressure • atmosphere

Nutrients • Required by all living things • Many serve as energy sources • Vary from species to species • May be sources of C, O, H, N, P, S

Moisture • Required for all living things • Cells contain 70 -95% water • Metabolic activities require water • Dessication • Some stages of microbial life can survive dessication • endospores

Temperature • Optimum growth temperature • Minimum growth temp • Maximum growth temp • Differs from species to species • Thermophiles • Mesophiles • Psychrophiles

p. H • Acidity or alkalinity of a solution • Most microbes prefer neutral • Acidophiles prefer low p. H • Stomach • Pickled foods

Osmotic Pressure & Salinity • Pressure on cell membrane from within & without • Ideally, isotonic

Movement of Solutions • Cell membranes are semipermeable • 6 processes govern movement of solutions into & out of cells • 3 passive • 3 active

Diffusion � Molecules scatter themselves equally throughout their environment; equilibrate � Movement is from an area of greater concentration to an area of lesser concentration � Examples �Ammonia-soaked rag �Oxygen is more concentrated in blood than in cells �https: //www. youtube. com/watch? v=f. C 66 AEz. P_0 M

Osmosis • Diffusion through semi-permeable membrane • Some solutes can diffuse through membrane, some can’t • Example • Tea bag • https: //www. youtube. com/watch? v=0 c 8 ac. UE 9 Itw

Osmosis in relation to RBCs • Isotonic solutions • Hypertonic solutions • Hemolysis • Crenation • https: //www. youtube. com/watch? v=7 -QJUUX 0 i. Y

Filtration • Determined by the size of the molecules • Example • Kidneys • https: //www. youtube. com/watch? v=7 -QJ-UUX 0 i. Y

Active Processes • Active transport • Requires ATP • Across concentration gradient • Hyperbaric oxygen chamber • Phagocytosis • Cell eating; white blood cells • Pinocytosis • Cell drinking; substances within solution

https: //www. youtube. com/watch? v=2 -ic. EADP 0 J 4

Gaseous Atmosphere • Microbes vary according to oxygen needs • Obligate aerobes • Microaerophiles • Obligate anaerobes

Encouraging in vitro Growth • Materials used to culture bacteria in the lab • • • Petri dishes Culture media Bunsen burners Inoculating loops Stains incubators

Bacterial Growth Increase in population Binary fission -- 2 daughter cells Colony Reproduction continues until nutrients & water are depleted, or waste products become toxic • Generation time; varies with species (slow growers/fast growers) • http: //www. youtube. com/watch? v=DY 9 DNWcqx. I 4 • https: //www. youtube. com/watch? v=g. Ewz. Dydci. Wc • •

Binary Fission

Influence of Culture Media on Growth • We can control environment (temp, ph…) • Fastidious bacteria • Obligate intracellular parasites won’t grow on inanimate media • Viruses • Chlamydias • rickettsias

Culture Media • Artificial media • Liquid, solid • Enriched media • Selective media • Inoculating culture media; • liquid vs solid

Sterile technique for Inoculation • Excludes all microbes • Plated media are kept sterile other than during inoculation • Contaminants, contaminated • Use of a control https: //www. youtube. com/watch? v=370 xx. Vcujyg

Incubation • Refers to the “growing” phase • May take place in a chamber called an incubator • Optimum temp for human pathogens

Bacterial Population Growth Curve � Lag phase �Prepare for reproduction by absorbing nutrients � Log phase �Rapid growth; population double with each generation time � Stationary phase �Growth rate slows as resources are used up & toxins build up � Death phase � https: //www. youtube. com/watch? v=Bs. PKc. HSh. G Yw 5 min

Growth Curve

Week 6 Episode 3 Preventing bacterial growth

Three levels of preventing microbial growth • Sterilization • Disinfection • Sanitization

Sterilization • Complete destruction of microbes • Dry heat • Autoclaving • Gas • Chemicals • radiation

Dry heat for sterilization

Moist heat for sterilization - Autoclave

Chemical Sterilization • Microbicides • Microbistatics

Microbicides • Germicides, microbicides kill microbes • Bactericides kills specifically bacteria • Sporicides kill endospore-forming bacteria • Fungicides • Algaecides • virucides

Disinfection � Removal of pathogens from inanimate objects � Physical or chemical � Pasteurization � Disinfectants- strong chemicals not used on living tissue � Antiseptics are used on living tissue � Sanitization- reduction of microbes to levels considered safe in public health

Chemicals Used to Inhibit Growth • Disinfectants • Affected by prior cleaning of surface, # & type of microbes present, concentration of disinfectant, contact time, temperature & p. H • Most vegetative bacteria are susceptible to disinfectants; endospores resistant • Antiseptics • Used on living tissue • Reduces # of organisms present

Microbistatics • Inhibit the growth of microbes • Bacteriostatic agents • Lyophilization

Antiseptic Techniques • Sepsis- pathogens in blood or tissue • Asepsis- absence of pathogens • Antiseptic technique- Lister • Sterile technique excludes ALL microbes

Physical Inhibition of Microbial Growth � Heat � Thermal death point-lowest temp that will kill � Thermal death time-time needed at temp � Material being sterilized must be considered (liquid, solid, wrapped) � Dry heat- metals, glassware, powders � Incineration- flaming loops � Moist heat- vegetative forms killed by boiling � Endospores require autoclaving or Tyndallization

Other Physical Methods to Inhibit Growth • Metabolism slowed by cold or freezing • Dessication • Radiation • Sun, UV lamps • Filtration • HEPA filters • Controlling gaseous atmosphere • Hyperbaric oxygen

Hyperbaric Oxygen Chamber

Quick Review • Name the conditions that are important for microbial growth. • Name 4 items needed for promoting the growth of microbes in vitro. • What are the 3 levels of preventing microbial growth? • What is the difference between in vitro and in vivo?