Bacteria

The faster a bacterial cell can get atoms into its cell, the faster the cell can grow, so the sooner it will get large enough to divide, so the faster it will reproduce, and so the faster the bacterial population will increase, so the faster the bacterial colony will 'grow'.

Bacteria are made up of atoms

To get bigger they need more atoms!

To get more atoms they eat things.

Bacteria eat by simply absorbing nutrients straight through their cell membrane

This might seem weird, but that is how all of our cells get their nutrients, our cells absorb them through their cell membrane. With the nutrients coming from the blood

Even in our intestine, the nutrients are absorbed through membrane of the cells of the villi in the small intestine

So, its a normal way for cells to get their nutrients, they absorb them

The movement of the nutrients to the cells is through concentration gradients. Usually once a nutrient is inside a cell

To digest food, the bacteria release digestive enzymes. These digestive enzymes move through to the substance to be digested and break it down, releasing small nutrients that dissolve in water and move down their concentration gradient. Away from where they are in high supply near the food, towards the bacteria that absorbs them through its membrane, thus making the nutrients 'disappear' and maintaining the concentration gradient

Growth of individual bacteria, or growth of the colony through the rate of reproduction (reproductive rate).

These are affected by the environment.

Temperature is a good example of a abiotic environmental factor that can effect growth of both individual bacteria and growth of the colony (reproductive rate)

As the environment gets warmer, the molecules in liquids speed up.

Water moves faster and the substances floating in the water speed up

Increase in temperature increases the kinetic energy of particles

The enzymes slam into the food source faster

The enzymes have more energy, the quickly bend the food source allowing the chemical reaction (usually hydrolysis) to occur splitting the food into smaller nutrients

Because water molecules are moving faster, these nutrients are carried in the water to the bacteria faster

They are absorbed into the bacteria faster and become part of the bacteria faster.

Because the bacteria is absorbing atoms faster, it grows faster

As it grows faster, it gets to the size required for splitting faster.

The bacteria thus splits into two. Thus reproduction via binary fission has occurred sooner.

So the number of bacteria doubles sooner.

Because molecules are moving faster, everything happens faster.

But there is a limit

At temperatures closer to 50 degrees, the water molecules are moving so quickly that they shake the enzyme

The water molecules shake the enzyme so hard that its weaker hydrogen bonds break and the enzyme changes shape

This is 'denaturing'. A denatured enzyme no longer works.

Because the chemical reactions of life are conducted by enzymes, broken enzymes slows everything down.

As more enzymes are denatured, things slow down more, until the processes of life can no longer occur, and the bacteria die

This is one of the reasons that we cook our food.

(The other reason we cook our food is to begin to hydrolyze cellulose, starch and proteins - in other words, to make the food softer and easier to eat)

pH can also denature proteins by breaking hydrogen bonds in the proteins. This is how our stomach acid kills bacteria

This food safety poster actually covers all the things that bacteria need to survive!

Food - Nutrition

Acidity -pH affects the bacteria

Time - time for the colonies to grow and get up to their exponential phases and their stationary phase

Temperature - the closer to human body temperature the faster the bacteria multiply

Oxygen - some bacteria breath oxygen

Moisture - bacteria need moisture in order to get dissolved nutrients into their cells from the environment

Bacterial spores

When nutrients or water start to run to low to sustain the life of a bacterial cell , some 'spore forming' bacteria, like Anthrax, will form a spore.

The bacteria spore forming bacteria will make just one spore. The spore will only be 'free' once the rest of the bacterial cell degrades. Because 1 spore forming bacteria will make 1 spore, this is not reproduction, rather it is a long term survival strategy of the individual bacteria.

Imagine that during the COVID pandemic, you could just put your body into storage, as a head and nothing more. Once the pandemic was over you then regrew your torso, arms and legs and then carried on. So effectively the bacteria regrows from its spore once conditions are 'favorable'. This is why this is listed under growth

The spore contains a copy of the bacteria's DNA. The spore is dormant - it does not conduct respiration, all of the enzymes stop moving too and the spore waits for moisture and nutrients to diffuse into it, then it will turn back on respiration, the enzymes will start moving and the spore will grow into a bacterial cell.

Some bacterial spores can survive cooking and they can survive for years, depending on the species.

Respiration

Respiration is the process of breaking down large compounds, releasing chemical potential energy, and using this energy in the cell

This is related to breathing, in that for us we need oxygen to do this process

For use we combine a hydrocarbon (big compound) with oxygen, to make carbon dioxide (small compound) and water (small compound)

Whenever you combine small compounds together to make big compounds you need to put a lot of energy in

Think of building a brick wall by yourself. Putting each brick in takes energy.

Whenever you break big compounds back down to small compounds you need to put in a small amount of energy, but you get a lot of energy out of the big compound

Think of using a sledgehammer to breakdown the wall. A small amount of energy to start it falling, a huge amount of energy out as it falls down.

This relates to activation energy and energy graphs below

When compounds with lots of atoms are made from compounds that have few atoms, a lot of energy has to be put in. Some of that energy stays in the big compound.

In other words, it takes lots of energy to build complex compounds from simple compounds and some of that energy is stored in the complex compound as chemical potential energy.

When a big compound with lots of atoms is broken down into smaller compounds with fewer atoms, energy needs to be put in to start the reaction, but lots of energy is then released from the big compound

In other words, it takes some energy to start to deconstruct complex molecules into simple molecules, but that deconstruction releases lots of stored chemical potential energy

This is much like building a brick wall, and then pushing it over.

Building by hand takes lots of energy. Pushing it over takes some energy. When it crashes down and brakes back into bricks we hear that energy being released.

Photosynthesis makes the complex compound glucose from the simple compounds carbon dioxide and water.

To make glucose, energy from light is put in. Some of the energy put in is 'lost' as heat. Some remains within the molecule.

So glucose contains more chemical potential energy than water and carbon dioxide.

Ultimately the energy to make all complex biological compounds, and all life, comes from the sun!

When we break that complex glucose back down to Carbon dioxide and water, the stored energy within the molecule is 'released'.

This energy is then used to power other chemical reactions in the cell and to allow other compounds (like enzymes) in the cell to do stuff, like build even bigger an more complex molecules

Often this energy is used to join a phosphate onto Adenosine Diphosphate, to make Adenosine Triphosphate.

ADP + P + Energy = ATP + stored energy

Aerobic Respiration

All biological molecules contain Carbon.

This Carbon enters living system as Carbon dioxide during photosynthesis and combines with Water to make a Carbohydrate (carbo = carbon, hydrate = water)

Enzymes in plants and in photosynthetic bacteria turn these carbohydrates into fats and into amino acids for proteins

These carbon based structures can be 'burnt'. This involves taking oxygen and combining it with the Carbon to remake Carbon dioxide. What is left over is water.

Through this process, the large carbohydrate glucose (sugar) is broken into smaller carbon dioxide and water compounds. This releases chemical energy for the cell to use

This form of respiration is called 'Aerobic' respiration because it uses the air.

This is like an Aeroplane. An aeroplane uses the air

More specifically though, Aerobic Respiration uses oxygen

Aerobic respiration breaks the carbohydrate glucose down to the smallest possible compounds, thus it releases the most energy from glucose.

In other words, aerobic respiration releases the highest amount of energy possible

Composting

Composting involves Bacteria conducting Aerobic Respiration. Through this process, your pile of compost gets smaller as the cellulose and starches form the discarded plants and food scraps (grass clippings, fruits and vegetables) is digested into glucose and then combined with oxygen through aerobic respiration and converted back into Carbon Dioxide and Water.

This is why you can see steam rising from your compost pile when it is a cold morning and why there is water on the inside lid of the compost bin.

This is also why the glad wrap is wet on the inside, when you find that sandwich from last term at the bottom of your bag.

In your compost bin there are usually air grates throughout it. This is to get air and oxygen into the bacteria that is eating the grass and food waste.

These bacteria turn your compost into Carbon dioxide and water, leaving behind a mineral rich mush that contains very large compounds that are still being digested - this is soil.

Waste Water Treatment

If we look at Waste Water (sewage) we see that there is a lot of carbon compounds in the water. This is because we eat carbon compounds and about 1/5th of what we eat leaves as feces (the rest is burnt by cellular respiration or stored as fat)

By letting bacteria feed on this feces, it turns the carbon based waste (such as fiber in feces) back into Carbon Dioxide and Water. This is why if an deer poops in the woods, eventually its poop will disappear

To speed up this feeding and respiration, the pond of waste is bubbled with air.

This is done in the 'aeration tank' or 'oxidation pond'. These are the same things, it just depends on the country you are in.

This helps the bacteria to get oxygen so that aerobic respiration will happen

You can see the oxidation ponds, or aeration tanks in the picture above, the big circles. Notice the white around the outside from all the bubbles of air. Interestingly only the outside is full of air.

The sewage treatment plant will also use Anaerobic respiration to reduce the amount of nitrogen and to produce methane for electricity production

The amount of methane produced is enough to meet all of the electricity requirements of the plant, and still have electricity for houses

On the handout below the focus is on the 'Reactor' and the 'Clarifier'. These are the two parts of the large tanks seen on google maps and in the images of the Mangere wastewater treatment plant.

Water enters into the outside 'reactor' part, here the water alternates between bubble filled aerobic zones where air is bubbled in so that aerobic bacteria can use the oxygen for aerobic respiration and they can turn carbon compounds into carbon dioxide and water.

Then the water moves to the anoxic zones. Anoxic means no oxygen. Here there is no added air, so the oxygen levels deplete. The methanogenic bacteria here use nitrate, NO3, as a source of oxygen to make methane and nitrogen gas, while other anaerobic bacteria just make lactic acid

Then the water moves back into an aerobic zone and aerobic bacteria take over again

This back and forth process ensures that the carbon compounds get smaller and smaller as they are attacked, digested and absorbed by different bacteria. It also helps to reduce the nitrogen levels, which is important to stop algae blooms when the water is finally released into the Manukau Harbor.

Mangere Sewage Treatment Plant further information

Sewage treatment is similar the world over. It always uses bacteria to turn carbon compounds into carbon dioxide. The clip above shows how wastewater is treated in New York City and below is London

Mangere Sewage Treatment Plant further information

Anaerobic Respiration

Anaerobic Bacteria do not use oxygen (anaerobic - an no air)

So, no oxygen

The big carbohydrate compound (glucose) can still be broken down into smaller compounds to release stored chemical energy

But it can't be broken all the way down to Carbon dioxide, because there is no dioxide to bind the carbon onto

Breaking down carbohydrates without oxygen is also called Fermentation

Anaerobic Bacteria will do Lactic Acid Fermentation

The big 6 carbon carbohydrate, glucose, is broken down into two 3 carbon compounds called Lactic Acid. This releases only a small amount of energy

Anaerobic Respiration

C₆H₁₂O₆ = C₃H₆O₃ + C₃H₆O₃ + Chemical Energy released

Glucose = Lactic Acid + Lactic Acid + Chemical Energy released

Notice that the number of atoms and the number of each type of atom in Lactic Acid is exactly half that of Glucose

C₆H₁₂O₆ = C₃H₆O₃ + C₃H₆O₃

Yogurt

This Anaerobic Respiration by bacteria creates lactic acid

Acid causes the proteins in milk to denature. This makes milk clumpy.

If you leave your milk for ages it will go off, it will smell and it will be clumpy - due to lactic acid and lots of different bacteria releasing toxins

But with fresh milk, you can heat it to denature the proteins with heat, then add a species of bacteria called lactobacillus. This will do anaerobic respiration and release lactic acid. The lactic acid will make the milk thick - this is yogurt.

(Once different bacteria get into the yogurt, it will go off due to different toxins being released by the other bacteria)

Note, that the bacteria doesn't have to use glucose as the hydrocarbon for this process. In yoghurt the bacteria can also use the sugar Galactose C₆H₁₂O₆

In the anaerobic fermentation of fruits by bacteria, they will use the sugar Fructose, C₆H₁₂O₆

Notice that these sugars still have the same number of atoms and of each atom as glucose, C₆H₁₂O₆. Its only the exact arrangement of these atoms that differ. Because they all have the same number of each atom, they can all be split by anaerobic bacteria into Lactic Acid, C₃H₆O₃

Methane

Some bacteria can turn glucose and other carbon compounds into an even smaller compound, the 1 carbon 4 hydrogen compound; Methane.

These bacteria will take the hydrocarbon, and make Methane CH₄ and Water H₂O

This is used in Landfills to generate Biogas to then burn for electricity

Bacteria that can make Methane though anaerobic respiration are called Methanogenic bacteria (methane making (genesis).

You have some methanogenic bacteria in your large intestine, which is why farts contain methane!

Denitrifying bacteria

Some bacteria can use Nitrate NO3 in the place of oxygen

This is still anaerobic respiration, as there is no oxygen

These bacteria are called denitrifying bacteria

These denitrifying bacteria are important for the cycling of nitrogen through the environment

They are also important in sewage treatment plants

Obligate vs Facultative

Obligate means obliged, I'm obliged to do something

Facultative means to facilitate, I can facilitate either request

We can then pair these terms with aerobic and anaerobic

Obligate Aerobe

- - - - has to have oxygen (like us)
      - obligated to do aerobic respiration
      - has compounds and enzymes that bind to oxygen ions that are released during aerobic respiration - Catalase and superoxide dismutase
      - (these oxygen ions, also known as free radicles and reactive oxygen species, are all the same thing, it is an individual oxygen ion. These will bind to anything in the cell and are the main cause of our aging. This is why it is important to eat fruits, vegetables and berries that are high in anti-oxidants)

Facultative Anaerobe

can facilitate both types of respiration
can use oxygen for aerobic respiration
can facilitate anaerobic respiration if it has to

Obligate Anaerobic

does not use oxygen
obligated to do anaerobic respiration
Oxygen can be toxic to some obligate anaerobes as they wont have any antioxidant compounds to bind to oxygen ions

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