The bacteria surround us in this world. The humankind has basically lived with bacteria throughout the whole history. There are Bacteria are microscopic, single-celled prokaryotes. The bacteria were discovered by Anthony van Leeuwenhoek. During the late 1600’s, Anthony was the first one to study bacteria.Cellular StructureThere are structures that benefit the bacteria. Capsule is the preservative covering, made of complex carbohydrates. Then there is the cell envelop. It is made of two to three layers, which are the inside of cytoplasmic membrane, cell wall, and sometimes the outer capsule. Cell wall gives shape and surrounds the cytoplasmic membrane. It holds and attaches pili and flagella. Cytoplasm is where the functions for cell growth, metabolism and replications happens. Cytoplasm holds organelles in place. Cytoplasmic membrane, also known as the Plasma membrane, is a layer of phospholipids and proteins. It surrounds the inside of the bacterium and manages the flow of materials both in and out of the cell. Flagella is hair-like structures that helps the bacteria move around. Pili is small hair-like structure sticking out from the outside cell surface to help the bacteria attach to other cells and surfaces. Ribosome creates protein.MetabolismMetabolism is the term used to describe all the chemical reactions inside a cell. Organisms are able to be classified according to the source of carbon they use for metabolism as well as their energy source. Organisms that change inorganic carbon dioxide into organic carbon compounds are called autotrophs. Organisms that obtain fixed carbon from organic compounds created by other organisms are named heterotrophs. Furthermore, we can categorize organisms by where they obtain their energy. Organisms that use light as the source of energy are named phototrophs. Organisms that use chemicals as the source of energy are called chemotrophs.Growth and ReproductionBacteria reproduce asexually in a process named “Binary Fission”. Binary fission is when single celled organism divides into two identical single celled organisms. The binary fission steps start as the cell grows. Then the DNA is copied and attaches to the cell membrane. Next, the DNA and its copy separate, and the cell grows larger. Finally, the cell splits into two. Now the both cell has identical DNA. The growth of bacterial population happens in a geometric or exponential growth. With each division cycle, one cell ascends to 2 cells, then 4 cells, then 8 cells, and goes on. They are basically doubling themselves. There are the phases of bacterial growth. Lag phase, log (exponential) phase, stationary phase, and the death phase. During the lag phase, the bacteria are getting used to their surroundings. They synthesize enzymes, proteins, RNA and many more. They increase in metabolic activity. During the log (exponential) phase pattern of growth has rapidly increased. If the bacteria are pathogenic, this would be the time that disease symptoms occur. Next is the stationary phase. During this phase, the number of viable bacteria cells remains the same. The rate of bacterial growth is equal with bacterial cell death. After the tiring rapid cell division, nutrients would be consumed, and toxic products will be set free. The cell division cannot continue at the same pace if it is more difficult to find nutrients and face the toxins. The final phase is the death phase. During this phase, the decline in population occurs. The number of viable cells reduces exponentially.