Microbes

Bibhabasu MohantyAsst. Prof. Dept. of civil Engineering

SALITER, Ahmedabad

Content…

Types of microbes, Growth and

their role in 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 harmful

Are vital for life on Earth.

What do Microbes look like ?Magnified 1000’s of times and coloured usingdye, we see -

Microbes exist in huge numbers

In 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 us

In our foodCleaning up our wasteKilling pestsMaking medicinesIn the making of such things as

leather, soy sauce, cheese and paper.

In our bodies.

Types of Microbes

Named 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 Description

Psychrophile/facultative psychrophile

Optimal temperature for growth is 15 °C or lower, maximal temperature is approximately 20 °C, and minimal temperature is 0 °C or lower

Psychrotroph Capable of growing at 5 °C or below, with maximal temperature generally above 25 °C to 30 °C

Mesophile 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 °C

Thermophile Grows at 50 °C or above

Hyperthermophile

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 Description

Acidophile Grows at pH values less than 2

Alkalophile Grows at pH values greater than 10

Neutrophile

Grows best at pH values near 7

Salinity Description

Halophile 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 NaCl

Hydrostatic pressure(100 atmospheres per 1,000-m depth)

Description

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 Description

Autotroph Uses carbon dioxide as its sole source of carbon

Heterotroph Unable to use carbon dioxide as its sole source of carbon and requires one or more organic compounds

Chemoorganoheterotroph

Derives energy from chemical compounds and uses organic compounds as a source of electrons

Chemolithoautotroph

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 chemolithoautotrophically

Oligotroph Can develop at first cultivation on media containing minimal organic material (1 to 15 micrograms carbon per liter)

Microbes – three types

Bacteria strep bacteria

Virus rotavirus

Fungi mould

BacteriaHave three main shapes

spiral (boriella) little balls(-cocci) rods (-bacilli)

Can move about on their own

Join up together to form chains called ‘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 Microbes

Algae 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 Growth

refers 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 grow

For 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 Growth

Temperature– 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

pH

Most bacteria grow between pH 6.5 - pH 7.5

Very few can grow at below pH 4.0many foods, such as sauerkraut, pickles, and cheeses are preserved from spoilage by acids produced during fermentation

Factors that Influence Growth

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 Pressure

Microbes obtain almost all their nutrients in solution from surrounding water

Tonicity– isotonic– hypertonic– hypotonic

Factors that Influence GrowthMacro & Micro Elements

C HOPKINS CaFe Mg NaCl

Limiting factors in the environment

Lack of food, water or nutrientsspaceaccumulation of metabolic wasteslack of oxygenchanges in pHtemperature

Phases of Growth

4 Phases

1. Lag Phase2. Log Phase3. Stationary Phase4. Death Phase

Lag Phase

Bacteria are first introduced into an environment or media

Bacteria are “checking out” their surroundings

cells 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 reproduction

Due to limiting factors in the environment

Roles of microbes in environment

Microbes—life forms too tiny to see—play a

surprisingly 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 life

Invite a microbe to dinner

Nature’s master chemists

New possibilities

Microbes keep our planet healthy

Liveable climate.

Healthy farms

Cleaning up

Productive ecosystem

Any Questions?