Making a Bacterial Cell – Bacteria

by Vincent Racaniello, PhD

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    00:01 Let's talk a little bit about how you make new bacterial cells. We focused so far on a single cell, but how do you get more. While the strategy for a bacteria is pretty simple, that cell grows and grows and it splits into two. So we start with one bacterial cell, we end up with two. That is called binary fission. Those two cells would in turn divide again, so we would go from 2 to 4 and from 4 to 8 and so on. So you can see that very quickly we will have a lot of bacterial cells. To make a new cell you have to make all the new components and this is a complicated process but we can simplify it for our discussion today. There are two general strategies for building new bacterial cells, there is what we called heterotrophy and that's where the bacteria has to get all the nutrients it needs, it can't make any of them, or there is autotrophy, where the bacteria can make a lot of the nutrients that it needs to build structures. And among the bacteria, some of them take carbon dioxide and an inorganic energy source and they can synthesize virtually everything they need.

    01:11 Other bacteria take CO2 and use light to make energy and all the compounds that they need.

    01:18 So we start by being either a heterotroph or an auxotroph, we then make what we call fueling products, the building components of the larger molecules, we take those and we make building blocks like amino acids, from those we can make macromolecules by polymerizing them like DNA or lipid. And finally we can take the macromolecules and build structures in the bacteria. So that's an overview of how all of this happens.

    01:48 Let's look at it in a little more detail, let's start with the fueling products.

    01:54 Bacteria have to make energy in the form of ATP and they use a hydrogen transport mechanism to generate the proton motive force in order to produce ATP. There are lots of precursor metabolites that are needed and some of these need to be acquired, some of them can be synthesized, they include a variety of sugars and acids like oxaloacetate and pyruvat. And finally we need reducing power in the form of NAD(P)H. These fueling products can be used to make the building blocks that are needed, like fatty acids for membranes, sugars, amino acids and nucleotides for DNA. Each of these then can be polymerized to make lipids, lipopolysaccharides, glycogen, murein, protein, RNA or DNA and these finally get built into bigger structures like inclusions, the envelopes in cell walls, flagella, pili, the actual cytosol itself, ribosomes and the nucleoid. In order to do this you require a variety of fueling reaction, so let's review how this works. I mentioned before that there are heterotrophic bacteria, they need to acquire all the components for fueling, they can't make them. These include chemoheterotrophs in which the source of carbon is an organic compound as well as the source of energy or photoheterotrophs in which the source of carbon is an organic compound, but the source of energy is light. Now you will see in the literature, heterotrophs sometimes being called organotrophs, so to alleviate confusion I've included that term here as well. So these are the heterotrophs, they need to acquire the fueling components, they can't make them. The autotrophs can make what they need, the chemoautotrophs use carbon dioxide as a source of carbon and their source of energy is an inorganic compound. The photoautotrophs use also carbon dioxide, but they can use light to make energy. These are the photosynthesizing bacteria. So an incredible variety of ways that bacteria can get energy and have a source of carbon to make other compounds. Bacteria can use as a carbon source, any natural organic compound on earth. This is more varied than any other living thing on the planet. The fact that they can utilize anything with carbon in it.

    About the Lecture

    The lecture Making a Bacterial Cell – Bacteria by Vincent Racaniello, PhD is from the course Microbiology: Introduction.

    Included Quiz Questions

    1. Binary fission
    2. Sexual reproduction
    3. Clonal proliferation
    4. Pinocytosis
    5. Binary fusion
    1. Organic nutrients
    2. Carbon dioxide
    3. Inorganic energy source
    4. Light
    5. Energy
    1. Glycol-6-phosphate
    2. Glucose-6-phosphate
    3. Fructose-6-phosphate
    4. Pentose-5-phosphate
    5. Erythrose-4-phosphate

    Author of lecture Making a Bacterial Cell – Bacteria

     Vincent Racaniello, PhD

    Vincent Racaniello, PhD

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