9/8/2016 Microbial number of cells Microbes compa ed with plants and animals. Bacteria may survive and grow slowly Invisible Invaders in nutrient- forming biofilms. Amazing Allies Biofilms may be sources of health bacterial colom core associated infections ASE Chapter 6 microbes that couse dise se or food Microbial Growth ilage ard how to encou Biofilm on plastic Serratia marcescen Physical Requirements for Growth Physical Requirements of Growth Temperature Learning Objectives Define groups into which microbes are Five groups based on optimum growth temperature placed based on their preferred 1.Psychrophiles-cannot grow at room temperature temperature range and preferred pH 2.Psychrotrophs-food spoilage at low Identify how and why the pH of culture temperatures media is controlled 3.Mesophiles-moderate-temperature:most Explain the importance of osmotic pressure pathogens and spoilage microbes of microbial growth 4.Thermophiles-important to compost piles: Survival and growth of any microorganism in a endospores and food spoilage,not a public health threat given environment depends on its metabolic characteristics. 5.Hyperthermophiles-extreme thermophile
9/8/2016 1 Invisible Invaders Amazing Allies Chapter 6 Microbial Growth • Microbial Growth – refers to the number of cells • Size of the microbe may double in size, but this is not very significant compared with plants and animals. • Bacteria may survive and grow slowly in nutrient-poor environments by forming biofilms. • Biofilms may be sources of health care associated infections • Microbial populations can become large in a very short time Scanning electron micrograph bacterial colony . • By understanding microbial growth, we learn how to control growth of microbes that cause disease or food spoilage and how to encourage growth of beneficial microbes. Biofilm on plastic Serratia marcescens Learning Objectives • Define groups into which microbes are l d b d h i f d Physical Requirements for Growth placed based on their preferred temperature range and preferred pH • Identify how and why the pH of culture media is controlled • Expp p lain the importance of osmotic pressure of microbial growth ______________________________________________________ Survival and growth of any microorganism in a given environment depends on its metabolic characteristics. Physical Requirements of Growth Temperature Five groups based on optimum growth temperature 1 . P h hil Psychrophiles – cannot t t t t grow at room temperature 2. Psychrotrophs – food spoilage at low temperatures 3. Mesophiles – moderate-temperature; most pathogens and spoilage microbes 4. Thermophiles- important to compost piles; endospores and food spoilage, not a public health threat 5. Hyperthermophiles – extreme thermophile
9/8/2016 Most common Refrigeration is the most common method of preserving food supplies. Based on the principle that microbial reproductive rates decrease at low temperatures. .Psychrotrophs do not grow well at low temperatures:however,they can slowly degrade food. Spoilage may be mold.slime.off-tastes or off- colors Refrigeration prevents the growth of most 30405动60 的0100 pathogens Food Preservation Temperatures Effect of the amount of food on its cooling rate in a refrigerator and its chance of spoilage 80 70 5nC5ae6 15 cm (6")deep
9/8/2016 2 Most common •Refrigeration is the most common method of preserving food supplies. •Based on the principle that microbial reproductive rates decrease at low temperatures se at low temperatures. • Psychrotrophs do not grow well at low temperatures; however, they can slowly degrade food. •S pg y oila ge ma y be mold, slime, off-tastes or offcolors •Refrigeration prevents the growth of most pathogens Effect of the amount of food on its cooling rate in a refrigerator and its chance of spoilage
9/8/2016 Physical Requirements of Growth pH pH-acidity and Acidophile Neutrophile alkalinity of a solution Bacteria grow best between pH 6.5-7.5 Few bacteria grow at a pH lower than 4 ·Foods such as pickles 11场0汤00场场 sauerkraut and some cheeses are preserved naturally 2.0 Physical Requirements of Growth Physical Requirements of Growth pH pH Alkalinity also prevents growth but is rarely used as a means of preserving food Bacteria produce acids as they grow.Media Molds and yeast grow over a wider pH range often contain buffers to maintain pH than bacteria but optimum is pH 5-6 Buffers are solutions that can resist changes in pH when acid or alkali are added Fungi Bacteria Phosphate salts used as non-toxic buffers Phosphate salts also provide nutrients for bacteria
9/8/2016 3 Physical Requirements of Growth pH • pH - acidity and alkalinity of a solution • Bacteria grow best between pH 6.5 – 7.5 • Few bacteria grow at a pH lower than 4 • Foods such as pickles, sauerkraut and some cheeses are preserved naturally Physical Requirements of Growth pH • Alkalinity also prevents growth but is rarely u m n f p ng f sed as a means of preserving food • Molds and yeast grow over a wider pH range than bacteria but optimum is pH 5-6 Fungi Bacteria Physical Requirements of Growth pH • Bacteria produce acids as they grow. Media often contain buffers to maintain pH • Buffers are solutions that can resist changes in pH when acid or alkali are added • Phosphate salts used as non-toxic buffers • Phosphate salts also provide nutrients for bacteria
9/8/2016 Physical Requirements of Growth Physical Requirements of Growth Osmotic Pressure Osmotic Pressure High osmotic pressure removes needed water from the cell Water is required for growth Hypertonic solution-water is lost causing Microbes are 80%-90%water plasmolysis or shrinking of the cytoplasm Microbes obtain most of their nutrients -Cell growth is inhibited in hypertonic from the surrounding water solutions Used as food preservatives-salted fish,honey.sweetened condensed milk Hypotonic solutions may lead to cell lysis Facultative halophile:do not require high salt to Hypotonic Hypertonic grow but can tolerate up to 2%NaCl Halophile-grows in high salt concentration Hatotolerant Halophie Extreme halophile Allvibrlo fischer Nad0.85% NaCl 10% Some bacteria require 30%NaCl Obligate halophile Norhaloohile requires high salt Growth of the to grow cell is inhibited
9/8/2016 4 Physical Requirements of Growth Osmotic Pressure • Water is required for growth • Microbes are 80% - 90% water • Microbes obtain most of their nutrients from the surrounding water Physical Requirements of Growth Osmotic Pressure • High osmotic pressure removes needed water from the cell • Hypertonic solution – water is lost causing plasmolysis or shrinking of the cytoplasm - Cell growth is inhibited in hypertonic solutions - Used as food preservatives – salted fish, honey, sweetened condensed milk • Hypotonic solutions may lead to cell lysis Hypotonic Hypertonic NaCl 0.85% NaCl 10% Growth of the cell is inhibited Facultative halophile: do not require high salt to grow but can tolerate up to 2% NaCl Halophile – grows in high salt concentration Some bacteria require 30% NaCl Obligate halophile requires high salt to grow
9/8/2016 Chemical Requirements for Growth Chemical Requirements of Growth Carbon Learning Objectives Carbon is the structural backbone of living Name a use for each of the four elements matter (carbon,nitrogen,sulfur,and phosphorus) One of the most important requirements for needed in large amounts for microbial microbial growth growth Half of the dry weight of bacteria is carbon Explain how microbes are classified on the basis of oxygen requirements Chemoheterotrophs get most of their carbon Identify ways in which aerobes avoid from organic substances damage by toxic forms of oxygen Chemoautotrophs and photoautotrophs derive carbon from carbon dioxide Table 27.1 Major Nutritional Modes Chemical Requirements of Growth 56rg Types of Organisms Nitrogen,Sulfur,Phosphorus Autotroph Light cO, .Nitrogen is mainly used to form amino acids plants;certain protists -Nitrogen makes up about 14%of the dry {《algae) weight of bacterial cells Chem Ccrt七ain prok otes(for autotroph exmpte,Suifolorus) .Sulfur-amino acids,vitamins .Phosphorus-nucleic acids,phospholipids,ATP Light Organic Certain prokaryotes terotroph -Sulfur and phosphorus together make up 4%of the bacterial cell Organic Organic pounds poun S
9/8/2016 5 Learning Objectives Chemical Requirements for Growth • Name a use for each of the four elements (carbon, nitrogen, sulfur, and phosphorus) needed in large amounts for microbial growth • Explain how microbes are classified on the basis of oxygen requirements • Identify ways in which aerobes avoid damage by toxic forms of oxygen Chemical Requirements of Growth Carbon • Carbon is the structural backbone of living matter • One of the most important requirements for microbial growth • Half of the dry weight of bacteria is carbon • Chemoht t h e erotrophs get t f th i b t most of their carbon from organic substances • Chemoautotrophs and photoautotrophs derive carbon from carbon dioxide Chemical Requirements of Growth Nitrogen, Sulfur, Phosphorus • Nitrogen is mainly used to form amino acids - Nitrogen makes up about 14% of the dry weight of bacterial cells •Sulfur – amino acids, vitamins • Phosphorus – nucleic acids phospholipids ATP nucleic acids, phospholipids, ATP - Sulfur and phosphorus together make up 4% of the bacterial cell
9/8/2016 Chemical Requirements of Growth Trace Elements Microbes require small amounts of other mineral elements .Trace elements:iron,copper,molybdenum,and zinc 2 .Function as cofactors and are essential for ATP activity of certain enzymes May be added to media but assumed to be found in tap/distilled water and other 000 Vitamin B1 components used to make the media Chemical Requirements of Growth Oxygen COFACTOR Me5thenisam9noEfegBoractnoreenergy Binding Obligate aerobe:only aerobic growth:oxygen required site Facultative anaerobe:both aerobic and araerobic growth: INACTIVE greater growth in the presence of axygen PROTEIN Obligate anaerobe:only anderobic growth:ceases growth in presence of oxygen Without the cofactor coestarbanieg Aerotolerant anderobe:only anaerobic growth:continues attached,the protein growth in presence of oxygen is not active. protein. Microaerophilic:only oerobic growth:oxygen required in low concentrations:lower than ai 6
9/8/2016 6 ATP Vitamin B1 Chemical Requirements of Growth Trace Elements • Microbes require small amounts of other mineral elements •Trace elements: iron, copper, molybdenum, and zinc • Function as cofactors and are essential for activity of certain enzymes • May be added to media but assumed to be found in tap/distilled water and other components used to make the media Chemical Requirements of Growth Oxygen Microbes that use molecular oxygen extract more energy from nutrients than those that do not. • Obligate aerobes are at a disadvantage since oxygen is poorly soluble in water • Obligate aerobe: only aerobic growth; oxygen required • Facultative anaerobe: both aerobic and anaerobic growth; greater growth in the presence of oxygen • Obligate anaerobe: only anaerobic growth; ceases growth in presence of oxygen • Aerotolerant anaerobe: only anaerobic growth; continues growth in presence of oxygen • Microaerophilic: only aerobic growth; oxygen required in low concentrations; lower than air
9/8/2016 How oxygen does harm Toxic Oxygen Toxic forms of oxygen 1.ingletyis normal molecular xy booted into Singlet oxygen a higher energy state that is very reactive 1O2 boosted to a higher-energy state 2.Superoxide ions are formed during normal respiration,all organisms growing in oxygen produces superoxide dismutase(SOD)which neutralizes it. Superoxide free radicals:O2 3.Hydrogen peroxide contains the toxic peroxide ion: produced during normal respiration.Microbes produce HSuperoxde dimutase H02+O2 catalases and peroxidases to neutralize it. 4.Hydroxyl radical is the most reactive form of oxygen Peroxide anion:O22- and is produced in the cytoplasm due to ionizing radiation. 2H202 Catalase一.2H,0+02 These toxic forms are an essential part of human's Hydroxyl radical (OH-) defense against pathogers as they are produce in the immune cells that take up bacteria and destroy them. H202+2H roxidase.2H Chemical Requirements of Growth Organic Growth Factors Organic growth factors are essential organic compounds that microbes are unable to synthesize. They must be obtained directly from the environment. .Examples:vitamins,amino acids,purine. pyrimidines >
9/8/2016 7 How oxygen does harm Toxic forms of oxygen 1. Singlet oxygen is normal molecular oxygen booted into a higher energy state that is very reactive 2.Superoxide ions are formed during normal respiration, all organisms growing in oxygen produces superoxide dismutase (SOD) which neutralizes it. 3.Hydrogen peroxide contains the toxic peroxide ion; produced during normal respiration. Microbes produce catalases and peroxidases to neutralize it. 4.Hydroxyl radical is the most reactive form of oxygen and is produced in the cytoplasm due to ionizing radiation. * These toxic forms are an essential part of human’s defense against pathogens as they are produce in the immune cells that take up bacteria and destroy them. Singlet oxygen 1O2− boosted to a higher-energy state Toxic Oxygen Superoxide free radicals: O2 Peroxide anion: O22– Superoxide dismutase O2 + O2 + 2 H+ H2O2 + O2 Hydroxyl radical (OH•) Catalase 2 H2O2 2 H2O + O2 Peroxidase H2O2 + 2 H+ 2 H2O Chemical Requirements of Growth Organic Growth Factors • O i th f t s Organic growth factors are ss ti l essential organic compounds that microbes are unable to synthesize. • They must be obtained directly from the environment. • Examples: vitamins, amino acids, purine, pyrimidines
9/8/2016 Biofilms Biofilms In nature,microorganisms seldom live as isolated single cells but instead live in multi- Learning Objectives cellular communities called biofms. Confocal microscope allows 3D visualization of Describe the formation of biofilms and the communities their potential for causing infection Reside in a matrix consisting of polysaccharide. protein,and DNA often called slime Cell-cell communication called quorum sensing allows the bacteria to coordinate their activity as a population Biofilms are organized into a coordinated,functional Clumps of bacteria community ering to surace are attached to surfaces-a rock in a pond,a tooth,or a mucus membrane consists of either a single species or a mixed species of bacteria. are a variety of shapes Bacteria in a biofilm -share nutrients are protected from harmful factors Water currents swap genetic information
9/8/2016 8 Learning Objectives Biofilms • Describe the formation of biofilms and their potential for causing infection In nature, microorganisms seldom live as isolated single cells but instead live in multicellular communities called biofilms. Biofilms Confocal microscope allows 3D visualization of the communities Reside in a matrix consisting of polysaccharide, protein, and DNA often called slime Cell-cell communication called quorum sensing allows the bacteria to coordinate their activity as a population Biofilms - are organized into a coordinated, functional community - are attached to surfaces - a rock in a pond, a tooth, or a mucus membrane - consists of either a single species or a mixed species of bacteria. - are a variety of shapes Bacteria in a biofilm - share nutrients - are protected from harmful factors - swap genetic information
9/8/2016 Biofilms in human health Biofilm on a catheter Biofilms-Good and Bad Microbes in biofilms are Beneficial Biofilms 1000x more resistant to antibiotics bacteria within biofilms CDC estimates that 70%of in the digestive system bacterial infections involve of ruminant animals biofilms breakdown cellulose Most nosocomial infections biofilms are essential are related to biofilms on for sewage treatment catheter systems -indwelling medical devices, including heart valves Normal flora of the oral cavity >contact lenses -dental caries confact ler Biofilms-Methods of Prevention Steps in Biofilm Formation -Incorporate antimicrobials into surfaces on which biofilms might form Planktonic bacteria: -Example:block the cell-cell communication free floating/swimming required for coordinating microbial activity Furanones embedded in plastic block biofilm formation
9/8/2016 9 Biofilms – Good and Bad Beneficial Biofilms - bacteria within biofilms in the digestive system of ruminant animals breakdown cellulose - biofilms are essential for sewage treatment systems Normal flora of the oral cavity Biofilms in human health - Microbes in biofilms are 1000x more resistant to antibiotics CDC estimates that 70% of Biofilm on a catheter - bacterial infections involve biofilms - Most nosocomial infections are related to biofilms on catheter dental plaque - indwelling medical devices, including heart valves contact lenses dental caries contact lens Biofilms – Methods of Prevention -Incorporate antimicrobials into surfaces on which biofilms might form -Example: block the cell-cell communication required for coordinating microbial activity Furanones embedded in pl bl k lastic block biofilm formation Steps in Biofilm Formation Planktonic bacteria: free floating/swimming
9/8/2016 Culture Media Culture medium:nutrient material prepared for growth of microbes in the laboratory Inoculum:microbes that are introduced into a Learning Objectives medium .Distinguish chemically defined and complex Culture:microbes that grow and multiply on a media culture medium Bacterial Cultures in Broth Media Justify the use of each of the following: anaerobic techniques,living host cells, candle jars,selective and differential media, enrichment medium Differentiate biosafety levels 1,2,3,and 4 What criteria must a culture medium Agar,a solidifying agent,is added to the meet to grow a microorganism? medium when growing bacteria on a solid medium. contain the right nutrients Agar is a complex polysaccharide derived contain sufficient moisture from marine alga and is used as a thickener in foods. contain the right amount of oxygen contain a properly adjusted pH must be sterile-contain no living organisms incubated at the proper temperature
9/8/2016 10 Learning Objectives Culture Media • Distinguish chemically defined and complex media •Justify the use of each of the following: anaerobic techniques, living host cells, candle jars, selective and differential media, enrichment medium • Differentiate biosafety levels 1,2,3, and 4 Culture medium: nutrient material prepared for growth of microbes in the laboratory Inoculum: microbes that are introduced into a medium Culture: microbes that grow and multiply on a culture medium What criteria must a culture medium meet to grow a microorganism? • contain the right nutrients • contain sufficient moisture • contain the right amount of oxygen • contain a properly adjusted pH • must be sterile – contain no living organisms • incubated at the proper temperature Agar, a solidifying agent, is added to the medium when growing bacteria on a solid medium. Ag p py ar is a complex polysaccharide derived from marine alga and is used as a thickener in foods