Microbes Bibhabasu MohantyAsst. Prof. Dept. of civil Engineering SALITER, Ahmedabad
Content…Types of microbes, Growth and their rolein environment.
MicrobesAre invisible to the naked eye, you need a powerful microscope to see them.Are everywhere around us, inside us, on us, in our food, in our homes, in the air we breathe and the water we wash in.Are mostly useful, but some are harmfulAre vital for life on Earth.
What do Microbes look like ?Magnified 1000‘s of times and coloured usingdye, we see -
Microbes exist in huge numbersIn one single teaspoon of garden soil, there are over 100,000 microbes. In 1ltr of seawater, there are over 1bn microbes.On your hands there are more microbes than there are people in the world.There are so many microbes, that scientists have only named 0.5% of them.Microbes outnumber all other species and make up most of the living matter on the planet.
Microbes live among usIn our foodCleaning up our wasteKilling pestsMaking medicinesIn the making of such things as leather, soy sauce, cheese and paper.In our bodies.
Types of MicrobesNamed based on their particular physiological and nutritional characteristics. Oxygen Description Aerobe Capable of using oxygen as a terminal electron acceptor Anaerobe Grows in the absence of oxygen Facultative anaerobe Can grow aerobically or anaerobically Microaerophile Capable of oxygen-dependent growth but only at low oxygen levels
Temperature DescriptionPsychrophile/ Optimal temperature for growth is 15 °C or lower,facultative maximal temperature is approximately 20 °C, andpsychrophile minimal temperature is 0 °C or lowerPsychrotroph Capable of growing at 5 °C or below, with maximal temperature generally above 25 °C to 30 °CMesophile optimal temperature for growth, which is approximately 37 °C; frequently grows in the range from 8 °C to 10 °C and from 45 °C to 50 °CThermophile Grows at 50 °C or aboveHyperthermophile Grows at 90 °C or above, although optimal temperature for growth is generally above 80 °C; maximal growth of pure cultures occurs between 110 °C and 113 °C,
pH DescriptionAcidophile Grows at pH values less than 2Alkalophile Grows at pH values greater than 10Neutrophile Grows best at pH values near 7Salinity DescriptionHalophile Requires salt for growth: extreme halophiles (all are archaea), 2.5 M to 5 M salt; moderate halophiles, usually low levels of NaCl as well as 15 to 20 percent NaClHydrostatic pressure Description(100 atmospheres per1,000-m depth)Barophile Obligate barophiles, no growth at 1 atmosphere of pressure; barotolerant bacteria, growth at 1 atmosphere but also at higher pressures. (0.987 atm = 1 bar = 0.1 megapascal [Mpa])
Nutrition DescriptionAutotroph Uses carbon dioxide as its sole source of carbonHeterotroph Unable to use carbon dioxide as its sole source of carbon and requires one or more organic compoundsChemoorganoheterotroph Derives energy from chemical compounds and uses organic compounds as a source of electronsChemolithoautotroph Relies on chemical compounds for energy and uses inorganic compounds as a source of electrons. hydrogen bacteria, iron bacteria, sulfur bacteria, ammonia oxidizers, and nitrite oxidizers.Mixotroph Capable of growing both chemoorganoheterotrophically and chemolithoautotrophicallyOligotroph Can develop at first cultivation on media containing minimal organic material (1 to 15 micrograms carbon per liter)
Microbes – three typesBacteria strep bacteriaVirus rotavirusFungi mould
Bacteria Have three main shapes spiral (boriella) little balls(-cocci) rods (-bacilli) Can move about on their own Join up together to form chainscalled ‗bio-films‘. As on teeth !
Virus Come in 1000s of different shapes and sizes. They hang about waiting to meet a ‗host‘ which they then invade, hijacking the host‘s cells. Beware the air you breathe and door handles !
Fungi Not just mushrooms – athlete‘s foot, penicillin, and yeast. Yeast is used in bread making, and brewing
Algae are also MicrobesAlgae photosynthesise – taking their energy from the sun, and producing oxygen in the process. Algae are thought to produce over 50% of the oxygen in the world.
And finally Without microbes, life on this planet would be entirely different – they generate oxygen, are part of the carbon and nitrogen cycles, and can survive the harshest conditions. Without microbes, our bodies would not process the food we eat. They drive the chemistry of life, breaking things down into their parts so that life can being again. Microbes are small but mighty !
Microbial Growthrefers to the no. of cells, not the size of the cells
Factors that Influence GrowthGrowth vs. Tolerance – ―Growth‖ is generally used to refer to the acquisition of biomass leading to cell division, or reproduction – Many microbes can survive under conditions in which they cannot grow
The suffix ―-phile‖ is often used to describe conditions permitting growth, whereas the term ―tolerant‖ describes conditions in which the organisms survive, but don‘t necessarily growFor example, a ―thermophilic bacterium‖ grows under conditions of elevated temperature, while a ―thermotolerant bacterium‖ survives elevated temperature, but grows at a lower temperature
Factors that Influence GrowthObligate (strict) vs. facultative ―Obligate‖ (or ―strict‖) means that a given condition is required for growth ―Facultative‖ means that the organism can grow under the condition, but doesn‘t require it The term ―facultative‖ is often applied to sub-optimal conditions For example, an obligate thermophile requires elevated temperatures for growth, while a facultative thermophile may grow in either elevated temperatures or lower temperatures
Factors that Influence GrowthTemperature – psychrophiles (cold loving microbes ) •range 0 C - 20 C – mesophiles (moderate temp. loving microbes) •range 20 C - 40 C – thermophiles (heat loving microbes) •range 40 C - 100 C
Factors that Influence Growth pH Most bacteria grow between pH 6.5 - pH 7.5 Very few can grow at below pH 4.0 many foods, such as sauerkraut, pickles, and cheeses are preserved from spoilage by acids produced during fermentation
Factors that Influence GrowthSalt concentration Halophiles require elevated salt concentrations to grow; often require 0.2 M ionic strength or greater and may some may grow at 1 M or greater; example, Halobacterium. Osmotolerant (halotolerant) organisms grow over a wide range of salt concentrations or ionic strengths; for example, Staphylococcus aureus.
Factors that Influence GrowthOxygen concentration – Strict aerobes: Require oxygen for growth (~20%) – Strict anaerobes: Grow in the absence of oxygen; cannot grow in the presence of oxygen – Facultative anaerobes: Grow best in the presence of oxygen, but are able to grow (at reduced rates) in the absence of oxygen – Aerotolerant anaerobes: Can grow equally well in the presence or absence of oxygen – Microaerophiles: Require reduced concentrations of oxygen (~2 – 10%) for growth
Osmotic PressureMicrobes obtain almost all their nutrients in solution from surrounding waterTonicity – isotonic – hypertonic – hypotonic
Factors that Influence GrowthMacro & Micro Elements C HOPKINS CaFe Mg NaCl
Limiting factors in the environmentLack of food, water or nutrientsspaceaccumulation of metabolic wasteslack of oxygenchanges in pHtemperature
Phases of Growth4 Phases1. Lag Phase2. Log Phase3. Stationary Phase4. Death Phase
Lag PhaseBacteria are first introduced into an environment or mediaBacteria are ―checking out‖ their surroundingscells are very active metabolically no of cells changes very little1 hour to several days
Log PhaseRapid cell growth (exponential growth)population doubles every generationmicrobes are sensitive to adverse conditions – antibiotics – anti-microbial agents
Stationary PhaseDeath rate = rate of reproductioncells begin to encounter environmental stress – lack of nutrients – lack of water – not enough space – metabolic wastes – oxygen – pH Endospores would form now
Death PhaseDeath rate > rate of reproductionDue to limiting factors in the environment
Roles of microbes in environmentMicrobes—life forms too tiny to see—play asurprisingly large role in life on Earth.Humans depend on microbial communities in more ways than you can imagine.
Make air breathableKeep us healthyProvide sources of new drugsHelp us digest foodClean up hazardous chemicalsSupport and protect crops
Microbes keep us healthyPartners for lifeInvite a microbe to dinnerNature‘s master chemistsNew possibilities