Microbial Metabolism Overview

Protein Catabolism

• Proteases and peptidases break down proteins into component amino acids
• Amino acids must undergo enzymatic conversion to enter the Krebs cycle

Metabolic Diversity

• Phototrophs use light as an energy source
• Chemotrophs use redox reactions of inorganic or organic compounds
• Autotrophs are self-feeders
• Heterotrophs feed on others
• Medically important organisms are chemoheterotrophic and infectious organisms that catabolize substances from the host

Impacts of Microbial Metabolism

• Disease and food spoilage
• Nitrogen cycle
• Beverages and food production
• Sewage treatment
• Drug production

Important Metabolic Processes

• Carbohydrate catabolism, lipid catabolism, and respiration are important for microbes

Carbohydrate Catabolism: Respiration

• Glycolysis is followed by the Krebs cycle and electron transport chain for ATP generation
• 38 ATPs can be generated from one glucose molecule

Carbohydrate Catabolism: Fermentation

• Krebs cycle and ETC are not required
• Produces end products like lactic acid or ethanol
• Two ATPs are produced from one glucose molecule

Lipid Catabolism

• Lipids are broken down by lipases into fatty acids and glycerol
• Each component molecule can then enter the Krebs cycle

Physical Requirements: Temperature

• Psychrophiles thrive in cold temperatures
• Mesophiles thrive in moderate temperatures
• Thermophiles thrive in warm temperatures
• Most bacteria grow within a limited temperature range of only 30°C
• Optimum temperature corresponds to the temperature allowing best growth

Physical Requirements: pH

• Most bacteria grow between pH 6.5-7.5
• Few bacteria can grow below pH 4
• Bacteria cultured in the lab often produce acids that interfere with growth
• Phosphate salts and peptones are chemical buffers used in lab

Physical Requirements: Osmotic Pressure

• Microbes obtain nutrients in solution from water
• Extreme halophiles thrive in high salt concentrations
• Obligate halophiles need high salt concentrations
• Facultative halophiles do not require high salt concentrations but can grow at concentrations up to 2%

Oxygen Requirements

• Obligate aerobes require oxygen
• Facultative anaerobes use anaerobic respiration or fermentation when oxygen is absent, like E. coli and yeasts
• Obligate anaerobes cannot use molecular oxygen for energy-yielding reactions, like Clostridium
• Aerotolerant anaerobes, like Lactobacilli, convert harmful forms of oxygen to O2
• Microaerophiles only tolerate oxygen concentrations lower than air

Chemical Requirements

• Carbon: structural backbone of living matter for organic compounds
• Nitrogen: forms the amino group of amino acids
• Sulfur: synthesis of sulfur-containing amino acids and vitamins like thiamine and biotin
• Phosphorus: synthesis of nucleic acids and phospholipids
• Trace elements: essential for some enzymes, sometimes as cofactors, and include iron, copper, molybdenum, and zinc
• Organic growth factors: essential compounds not synthesized, and include enzymes for vitamin synthesis, amino acids, purines, and pyrimidines

Culture Media

• Nutrient material prepared for the growth of microorganisms
• Microbes introduced into the medium to initiate growth are called inoculum
• Microbes that grow and multiply are called a culture
• Culture media must initially be sterile

Forms of Culture Media: Agar

• Agar is a solidifying agent
• Few microbes can degrade it
• Agar liquefies at 100°C and remains liquid until the temperature drops to 40°C
• Agar is not a nutrient

Forms of Culture Media: Broth

• Broth is a liquid culture medium
• Pellicle: mass is floating on top of the broth
• Turbidity: organisms appear as a general cloudiness throughout the broth
• Sediment: mass appears as a deposit at the bottom of the tube

Culture Growth

• Slants: tubes are held at an angle
• Stab tubes/deeps: bacteria gets inoculated by stabbing the medium
• Plates: Petri dishes are used in the culturing, separating, and counting of microorganisms
• MacConkey Agar: differentiates from lactose fermenters and non-fermenters
• Obtaining Pure Cultures: the streak plate method is most commonly used

Preserving Cultures

• Refrigeration is used for short-term storage
• Deep-freezing involves pure cultures in suspending liquid and quick-frozen at temperatures between -50°C to -95°C
• Lyophilization is freeze-drying, and involves quickly freezing microbes at temperatures ranging from -54°C to -72°C while removing water via high vacuum

5 I's of Culturing Microbes

• Inoculation involves producing a pure culture
• Isolation involves a colony on media and one kind of microbe growing a pure culture
• Incubation involves growing microbes under proper conditions
• Inspection involves an observation of characteristics
• Identification involves use of data, correlation

Microbial Growth

• Produces more cells, thus increasing microbial count
• Binary fission is the most common mode of reproduction
• Budding is another mode of reproduction

Sterilization

• Involves the removal or destruction of all living microorganisms

Disinfection

• Involves control of harmful organisms
• Antisepsis is disinfection directed at living tissue

Sanitation

• Lower microbial counts to safe public health levels and minimize chances of disease transmission

Aseptic Technique

• Protects from contact with biohazards
• Protects sample from contamination
• Protects others in lab

Control of Growth: Moist Heat

• Best for dishes and various equipment
• Autoclaving for media
• Kills all vegetative bacterial and fungal pathogens and almost all viruses within 10 minutes
• Autoclaving occurs at around 15 psi of pressure (121°C)

Control of Growth: Pasteurization

• Heat treatment that kills all pathogens and most non-pathogens
• Best for food preservation

Control of Growth: Dry Heat

• Direct: inoculating loops
• Incineration: paper cups, dressings
• Hot-air sterilization: empty glassware

Control of Growth: Filtration

• Separates suspending liquid from bacteria
• Best for sterilizing liquids, such as vaccines that can be destroyed by heat

Disinfection

• Few chemical agents achieve sterility, as most reduce microbial populations to safe levels
• No single disinfectant is appropriate for all circumstances

Disinfectants: Phenols and Phenolics

• Triclosan is a common example
• Can be put in disinfectant hand soaps
• Disrupts plasma membranes

Disinfectants: Biguanides - Chlorhexidine

• Used for skin and surgical disinfection

Disinfectants: Halogens

• Chlorine: forms -HOCl which alters cellular components

Disinfectants: Alcohol

• Protein denaturation occurs

Viruses

• obligate intracellular parasites
• non-cellular nature and are inert outside of the cell.

Virus Recognition

• Most viruses infection plants, animals and prokaryotes
• Virions contain A protein coat around the nucleic acid
• Most viruses infect only specific types of cells in one host
• The multiply by of the cell machinery

Host Range

• determined by specific sites and cell factor
• can determined by viruses and bacteria that interact in a unique way

Viral Structure

• composed of nuclaic acid and protein coat outside the host cell
• the are protected by capsid subunits

Viruses

• can be grown from animal or embryonated or through vaccines
• They contain a single type of acid
• They form from plaques a lawn of bacteria

Viral Taxonomy

• Nucleic Acid: the type of nucleic acid that is present in the virus
• Morphology: the physical structure and shape of the virus
• Strategy for replication: how the virus replicates its genetic material
• Symptoms: the symptoms caused by the viral infection
• Viral Species: viruses sharing the same genetic information and ecological niche

Viral Multiplication

• Viruses invade cells to reproduce
• Change the host cells and cause death
• consist of an Lytic Cycle and Lysogenic Cycle

Animal Viruses & Replication

• Latency- viral infection
• In DNA some enter thought nucleus and the virus replicates

Animal and Bacteriophages

• Contain proteins by fusion or receptor sites

Virus & Cancer

• Oncogenes: can be in animal cell in the tumor site
• Oncoviruses: capable in the tumor site

Viral Infection Factors

• include latent or persistent qualities to them can cause death
• includes measles. viroids or prions

Host Microbe Interaction

• the normal resident flora and antagonisms that occur to the host in different ways
• This can occurs by the normal biota that exists

Infection Factors

• Microbes and Pathogens can cause the host
• Can also produce Co operation among Pathogens Classifying infections can have contagious non contagious diseases
• Includes pathogens or vectors that exist

Stages & Levels of Duration

• can be latent and occurs from source on infection
• has the ability to cause the host harm or heal which could take time

Microbial & Virus Exits

• through the respitory , secretions , skin cells, through the fecal route . urogenital or through blood