Bacteria (and other single-cell nasty stuff)

Bacteria are also extremely tiny and abundant, although less abundant and less tiny than viruses, and the species range from necessary to deadly depending on the organism the bacterium is in and what species it is. The word "Bacterium" comes from "bakterion", Greek for "small staff", and they were named this because the first bacteria discovered were rod-shaped. They live inside and outside your body at all times when you are alive, and bacteria have caused some of the deadliest events in human history, most notably the Bubonic Plague and all its epidemics. Bacteria arose about four billion years ago, only five hundred million years after Earth was formed from a pile of dust, and single-celled organisms were the only living thing for more than three billion years, which was when the Cambrian Explosion came along, but that topic is irrelevant. Bacteria are classified by many things. Firstly, just like viruses, bacteria come mainly in three shapes. The groups this time are cocci (sphere-shaped), bacilli (rod-shaped), and spirochetes (spiral-like or helix-like). They are also classified based on whether they need oxygen or not (aerobic vs. anaerobic) and what color they turn after a stain is applied on them. Some bacteria are gram-positive, which means that they turn blue or purple after being stained, and some are gram-negative, which means they turn red or pink after staining. Lastly, bacteria can also reproduce incredibly quickly, just like viruses, but in a completely different way. Bacteria, you see, reproduce by something called binary fission, which is a fancy way of saying they split their body and DNA in half. This process involves a few steps, albeit that the process is simpler than viral reproduction. First, in the circular chromosome in the bacterium, there is an "origin of replication". Speaking of that chromosome, it gets "untangled" and takes up a much greater area during the replication process. Some bacteria also have plasmids, small rings of DNA separate from the main chromosome, and those get untangled as well. This is where the enzymes come along and the bacterium's DNA starts dividing; in more detail, it is the first part to be replicated, creating another origin. As the DNA is copied, the origins will move further away from each other, pulling the chromosomes along with them. Through this process, the cell will also be stretched longer and longer. Eventually, the cell will become long enough that a septum divides the cell in half and the halves can pull apart. This is similar to mitosis, the process where eukaryotic cells like our own divide.

Bacteria coming soon!