ENVI 003 Microbiology and Microbial Growth 2011[1] (1)

Microbiology and Microbial Growth

IntroductionMicroorganisms play

significant role in the natural environment and in engineered systems.

They are present in natural waters, serving beneficial purposes, yet posing the threat of disease when contaminated water sources are used for human consumption.

Antonie Van LeeuwenhoekThe first known recorded

microorganism were made by a Dutch linen merchant and amateur scientist Antonie Van Leeuwenhoek in l673.

Antonie Van LeeuwenhoekHe used a simple single-

lens microscope for his observations.

He sent detailed sketches of microorganisms with descriptive letters to the Royal society of London and was translated and published.

At that time no one realized that microorganisms were connected with disease. They were simply small creatures of interest.

Robert Koch Two centuries later, in

1876, a German physician named Robert Koch used the anthrax bacterium (Bacillus anthracis), to prove that microorganisms cause infections.

Robert Koch Koch observed that B.

anthracis a particularly large bacterium is always present in the blood of cattle with anthrax. But he asked, did the organism cause the disease, or the disease produce the organism?

Robert Koch Koch took blood from an

infected animal and injected it to a healthy animal.

The healthy animal then contracted anthrax. He repeated it 20 times and newly inoculated animals always get sick.

Robert Koch He even grew B.

anthracis on culture plates, thus he proved the germ theory of disease.

Robert Koch Koch’s work was

revolutionary and it led to many discoveries in the field of microbiology, including the causes of deadly diseases of the time.

Microorganisms Microorganisms of interest

to environmental engineers may vary from viruses, that pose general threat to human health to the specific waterborne protozoa, to bacteria that metabolize organic wastes in wastewater treatment systems.

Microorganisms Microorganisms are

present in almost imaginable place on earth. They are present in the soil, in the air, at the bottom of the ocean and in other life forms including humans.

pathogenic Microorganisms serve

beneficial functions; others pathogenic or disease-causing organisms, are harmful.

Two basic groups of microbesTwo basic groups of

microbes:1. Procaryotic – which

do not have cellular membranes. Procaryotes are single-cell organisms including only bacteria.

Eucaryotic1. Eucaryotic – maybe

single, or multicellular. They include algae, fungi, protozoa, and rotifers.

VIRUSViruses are considered a

separate group.

BacteriaBacteria – are unicellular

organisms that do not have a nuclear membrane. They vary in size from 0.1um. Their shape varies from cylindrical to spherical. Bacteria has a cell wall, membrane, cytoplasm, and DNA.

BacteriaMany bacteria have means

of motion flagella. These are single strands of hollow protein that the bacteria can rotate.

BacteriaAnother property of a bacteria

is their ability to produce endospores (internally produced spores).

Under these conditions the vegetative cell of a bacterial cell will form an endospore rather than divide.

Thus, spore formation is not a method of reproduction; instead a method of self-preservation.

BacteriaBacteria can live in many

places inhospitable places . Certain forms, for example can exist at the interface between water and fuel hydrocarbons fuel tanks. Others thrive in the depths of the oceans where hot water escape from fissures.

BacteriaStill others live in the

mouth and teeth of mammals, including humans.

And there are bacteria in our foods and water supplies.

VirusesVirus- the simplest form of life

known, exist in two forms; infectious particles that contain DNA and RNA, a structural coat; and some other chemicals. A viron particle contains nucleic acid and a capsule, or a nucleocapsid, termed as envelope.

When a virus infects a host, the nucleocapsid attaches to the host cell wall, and then the nucleic acid is the injected into the cell.

The viral nucleic acid then inserts itself in the host’s nucleic acid.

AlgaeAlgae are chorophyll-

containing eucaryotic organism that carry out oxygenic photosynthesis.

Most algae are microscopic, but some reach length of more than 100 feet.

AlgaeAlgae are important in

environmental engineering for many reasons.

They are responsible for taste and odor problems in public drinking water supplies originating in surface waters, particularly lakes.

AlgaeIn addition, algae generate

much of the suspended matter present in the effluent from lagoon wastewater treatment systems.

AlgaeAlgae are important in the

environment as primary producers of biomass.

Marine phytoplankton algae, are responsible for approximately 90% of photosynthesis on earth.

ProtozoaProtozoa are noteworthy in environmental

engineering primarily for their infectious nature and their role in the mixed microbial cultures of wastewater treatment system.

Protozoa are much larger than bacteria, and because they are predatory, they are motile (producing spontaneous motion).

One form of protozoa is the amoeba, a group characterized by flowing movement.

RotifersMulticellular

microorganisms called the rotifers prey on smaller microorganisms.

So they are of particular interest in wastewater treatment systems.

They act as “clarifiers” for such system by removing large quantities of dispersed bacteria. Their presence in water indicates a low level of pollution.

Metabolic ClassificationMicroorganisms can be classified by metabolic

processes ; such as their energy source, oxygen source, and carbon source for synthesis

1. Carbon source - all known life forms require carbon. Heterotrophic organisms obtain carbon from other organic matter or protein. Autotrophic organisms, that include plants and algae, obtain carbon for synthesis from inorganic carbon such as carbon dioxide and its dissolved species(the carbonates)

2. Oxygen source – Some microorganisms require molecular oxygen (O2), others this is toxic. Aerobic organisms or aerobes are those that require molecular oxygen (they are the oxygen that is present in the atmosphere, and oceans).

Anaerobic organisms do not require molecular oxygen. In fact molecular oxygen is toxic to them. This group includes several species of bacteria and some protozoa. These organisms require oxygen but they obtain their oxygen from inorganic ions such as nitrates, or sulfate or from protein.

Facultative organisms – prefer molecular oxygen but will use other pathways for energy and synthesis if if molecular oxygen is not available.

3. Energy source – energy is produced in cells

by either chemical or photo oxidation. A chemotroph obtains energy from the either

organic or inorganic.A phototroph obtains energy from light

metabolism of chemicals,, using photooxidation.

Microorganisms in the Environment Microorganism serve important and useful

purpose in the environment. Species of bacteria can convert atmospheric

nitrogen to ammonia (nitrogen fixation). This is important for some symbiotic bacteria associated with major crops.

Microorganisms are principal decomposers of waste material.

Microorganisms in the Environment In landfills, microorganisms degrade organic

wastes, producing simpler organics and eventually carbon dioxide, methane and water. In this process, the minerals contained in the waste return to the environment.

Microorganism represent a threat to human health or agricultural products. If not removed or killed in surface water sources used for human consumption, it can represent a significant health riisk.

Microorganisms in Engineered SystemMicroorganisms are widely used for

wastewater treatment; which are divided into two groups:

a) Bacteria attached to engineered surface –bacteria attached have evolved a complex chemical attachment system. They develop a slimy substance in their cell walls. A technical term for this layer of slime is a capsule or “glycocalyx”. In some cases, the glycocalyx is used by bacteria as a means of attachment to a host.

Slime layer cause rocks slippery; this layer term is biofilm.

Microorganism in this biofilm consume the waste, cleaning the water in the process.

Microorganisms in the Engineered Systemb) Bacteria remain suspended in the liquid being treated

– in the suspended growth system, the bacteria is suspended in the water in large tanks (or reactors). The bacteria move through the process with the water. The glycocalyx that enables bacteria to adhere to surface causes the suspended bacteria to stick to each other, forming large clumps or bacterial floc which settles faster than individual bacteria.

Microorganisms in the Engineered System Microorganisms are also being employed to

destroy toxic and hazardous wastes that have linked into the soil. In many cases, this requires the injection of essential nutrients into the soil to allow these organisms to thrive and grow.

MetabolismMicrobial metabolism – is the sum of the process

sustaining the organism, including both production of new cellular materials and degradation of other materials to provide energy.

Metabolism includes production of new cellular materials or anabolism; and the degradation of substrate to produce energy to maintain the cell or catabolism.

Microbial Growth Microorganisms use organic matter or substrate to

produce energy for replication, motility and repair of damaged cellular components.

When microorganisms are introduced into a closed system with unlimited source and substrate, there is a lag phase during which microorganisms adapt to the new substrate and concentration.

At this time, little microbial growth occurs. Once this initial phase is completed, organisms will begin a period of rapid growth, their numbers increasing exponentially. At some point, their population reach maximum.

Growth rate is proportional to the number of microorganisms. dx/dt = ux where x = concentration of microorganisms at time t t = time u = proportionality constant or specified growth rate, (time -1) dx/dt = microbial growth rate (mass/volume – time)

dx/x = udt

If concentration of organism is Xo at time zero,

ln{x/xo} = ut

Or x = xo eut

Assignment:A microbial system with an ample substrate and

nutrient supply has an initial cell concentration Xo of 500 mg/L. The specific substrate utilization rate is 0.5/hr.

a) Estimate the cell concentration after 6 hours, assuming growth is maintained during the period.

b) Determine the time required for the microbial population to double during this phase.