Eukaryotic cells and prokaryotic cells differ in many ways. From the size of the cells themselves, to the contents that are inside, the differences allow for all living organisms to be classified into these two categories. In order to identify unknown microbes, morphology, growth requirements, and biochemical reactions need to be known.
Prokaryotic & Eukaryotic Cells
Cells can be divided into two categories: prokaryotic and eukaryotic cells. Prokaryotic cells are significantly smaller than eukaryotic cells. This size difference is due to the many contents inside a eukaryotic cell that prokaryotic cells do not have. To begin with, prokaryotic cells are always going to be unicellular, while eukaryotic cells can also be unicellular but are many times multicellular (Murray & Baron, 2007). Prokaryotic cells do not have any membrane-bound organelles inside them, such as the nucleus, mitochondria, or lysosome as eukaryotic cells do. The DNA of eukaryotic cells is linear and is contained within the nucleus, while DNA in prokaryotic cells is circular and is contained within the nuclear body, a non-membrane surrounded structure (Murray & Baron, 2007). The number of ribosomes inside a prokaryotic cell is a lot less than those contained in a eukaryotic cell. Prokaryotic ribosomes are about 70s while eukaryotic ribosomes are larger, at 80s (Murray & Baron, 2007).
The differences between eukaryotic and prokaryotic continue as one goes more into detail with the specific structures. A eukaryotic cell has a cytoskeleton which is made up of microfilaments and microtubules, proteins that support the cell, transport essential proteins, and allow the cell to move; prokaryotic cells do not contain this feature at all (Murray & Baron, 2007). The mobility of a prokaryotic cell is possible because of their flagellum and not the tubulin that allows eukaryotic cells to move. Although eukaryotic cells also have flagella to ease movement, prokaryotic flagellum movement is rigid and rotates, while flagellum in eukaryotic cells is more flexible and has a wave-like motion (Murray & Baron, 2007). The reproduction processes between prokaryotic and eukaryotic cells also differ. While prokaryotic cells can also reproduce asexually, eukaryotic cells can divide both sexually and asexually. Prokaryotic cells divide through binary fission, while eukaryotic cells can divide through either mitosis or meiosis (Murray & Baron, 2007). Because of the lack of mitochondria in prokaryotic cells, the numerous metabolic pathways also vary between eukaryotic cell and prokaryotic cell (Murray & Baron, 2007).
Microbes are classified according to unique phenotypic features present in microorganisms. There are three phenotypic systems that can be used to classify microbes. The first is by the shape and size of the particular cell of the microbe (Murray & Baron, 2007). A gram stain or negative stain can be used in order to distinguish features that may not be visible by the naked eye. Through the specific morphology of the microbe, it can be phenotypically classified. This includes the size and shape of the microbe. A second system that can be used to phenotypically classify microbes is through their growth requirements (Murray & Baron, 2007). Some microbes are able to only grow in the presence of oxygen, while others will die if oxygen is present. Knowing the requirements of the microbe in question allows for easier classification. A third phenotypic classification system is classification through biochemical reactions (Murray & Baron, 2007). As some microbes grow, they emit certain enzymes that either effect the pH level of where they are growing or can only grow under particular conditions. Knowing the unique features of any microbe in question allows for better and more precise identification.
One of these microbes is the bacteria Clostridium botulinum. These bacteria can be immediately classified through a gram and/or negative stain. The morphology indicates that these bacteria are gram-positive so their cell wall only has a single peptidoglycan layer, allowing for the bacteria to stain dark purple; this allows for immediate classification into one of the two most common groups among bacteria (Nester, Anderson, & Roberts, 2012). Their morphology consists of a single rod-shape. Their oxygen requirements also allow for easy identification. They are obligate anaerobes, so they are only able to grow in areas where there is no oxygen present; with oxygen in their environment, they are unable to grow and reproduce and will most likely die (Nester, Anderson, & Roberts, 2012). The biochemical reactions that most classify Clostridium botulinum are by their neurotoxin production. As Clostridium botulinum are digesting nutrition in their environment they are able to continue to grow until they sense a reduction in their resources. When this occurs, Clostridium botulinum is able to form spores which allows for asexual reproduction by the pinching off of the bacteria's genetic material (Nester, Anderson, & Roberts, 2012). This ensures the survival of these bacteria despite a less than ideal biochemical environment.
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