Bacteria Exist Everywhere

1. The Microorganisms Family

Do you know what microorganisms are? They are a bunch of tiny creatures in nature with extremely simplified structures. Apart from some fungi such as mushrooms that are large enough to be seen, most microorganisms are invisible to the naked eye. To observe them, we must use a microscope to magnify their original sizes by hundreds or even hundreds of thousands of times. There are many different microorganisms in nature.Their presences are distributed out in various places and they are closely related to human beings.

If we were to compare a cell to a human, a cell's wall and membrane are like a person's skin.Cytoplasm is like blood and cellular organelles are just like various kinds of organs in the human body. The cell's nucleus is full of genetic materials, which can be passed down from the parent cells to offsprings.

How are all these microorganisms organized and classified? They are classified according to their sizes, structures and cellular components. Microorganisms are classified into three major groups, prokaryotic microorganism, eukaryotic microorganism and non-cellular microorganism.

1.1 Prokaryotic Microorganism

First, let's take a look at prokaryotic microorganisms. They only have a nucleoid instead of intact nucleus.What's more, their cell organelles areincomplete and the only organelle existing are ribosomes. Prokaryotes include bacteria, mycoplasma, chlamydia, rickettsia, helix, actinomycetes and etc.

Bacteria have the most amount of variation in species, and they are also the largest in numbers. Bacteria are tiny microorganisms with a simple structure. Outstanding scientists observed them under the microscope and discovered that some are spherical, which look like footballs, and we called them coccus.Streptococcus pneumonia and Staphylococcus aureus are examples of coccus. Others are rhabditiform named bacillus,such as Escherichia coli and Corynebacterium diphtheria. Some are spiral shaped, called spirilla, such as Helicobacter pylori.

Bacteria are composed of cytoderm, cytomembrane, cytoplasm and nucleoid. Some bacteria even have their own special structures, including capsule and spore, which can protect themselves from harm. The flagella help push themselves forward to move around, and fimbriae can help bacteria adhere to a host (Figure 1.1).

Mycoplasma is the smallest prokaryote. Without cytoderm, they can transform into various shapes just like plasticine, such as sphericity, rhabditiform, filiform, ramose and etc. An interesting fact, mycoplasma can grow on mediums prepared by scientists, and they look like delicious fried eggs when they are fully grown (Figure 1.2).

Just like parasites, chlamydia and rickettsia must live by other eucaryota since they are rather weak, therefore they cannot grow independently (Figure1.2). However, chlamydia goes through a special life cycle. Two different patterns are observed by scientists during the development of chlamydia, they are the elementary body (EB) and initial body (RB). EB is infectious and can easily infect the host cells. After entering into the host cells, EB can transform into RB, and then RB develops into EB, infecting new host cells to start another cycle.

Spirochetes and actinomycete both grow at a slow rate. Spirochetes are spindly in shape and extremely lively, often curling into a spiral. On the other hand, actinomycetes present filiform or dendroid like branches (Figure 1.2).

1.2 Eukaryotic Microorganism

Eukaryotic microorganisms' organelles and neucleus are relatively complete and intact. Take fungi as an example, they come in a variety of sizes.The smallest fungus is Crypto-coccusneoformans which can't be seen by the naked eye, while some large fungi are edible, such as mushroom and agaric.Fungi can be classified to unicellular fungi and multicellular fungi according to their structures.The first one is either round or oval in shape, the latter are composed of hyphae and spores (Figure 1.3). Fungi are not“picky” with their food, they are able to survive in all kinds of environment, but some grow very slow.

1.3 Noncellular Microorganism

Noncellular microorganism is a group of microorganisms that have the simplest structure and smallest in size. They do not have a complete celluar structure, neither can they live independently.Instead, they can only survive within other viable cells, just like a pagurian. The virus is a type of noncellular microorganism.

A mature virus particle is known as the virus body. Viruses have a variety of different sizes, and most viruses are spherical shaped or near-spherical, while a few of them are rod-shaped, filiform-shaped, or brick-shaped and etc. Virus does not have an integrated structure, with its nucleocapsid being the basic structure, it is composed by core and capsid. The core is similar to a cell nucleus and it is packed with genetic material. The capsid protects the core against all harm and danger. Some virus also has an extra structure called envelope outside the nucleocapsid. (Figure 1.4).