The+Bacterial+Cell

Bacteria Author: Ashley Hobson Posted: November 1, 2013

Bacteria are small, usually unicellular organisms that are deemed prokaryotes. Prokaryotic cells developed before and are smaller in size than eukaryotic cells, have no membrane bound organelles, and have a circular loop of DNA spread through the interior of the cell, called the nucleoid. Prokaryotic ancestry can be dated back 3.5 billion years ago. The domains Prokarya and Eukarya are found on the phylogenetic tree of life, shown below in Figure 1. Figure 1: Phylogenetic Tree of Life (  ) The prokaryotic domain includes both bacteria and archaea. Bacteria are separated into several different classifications, such as cyanobacteria (found in algae), thermotoga (which have a unique outer membrane, like a "toga"), and gram positive bacteria (which reacts with stain in a specific way). Some bacteria have cell walls for extra protection, especially if they are harmful. Modes of transport of bacteria range from the gliding motions of certain cyanobacteria to the well known flagella of bacteria such as Escherichia coli, shown below in Figure 2.

Figure 2: Escherichia coli cell diagram. ( [] )

Bacteria are usually single celled organisms, and are thought to be much older than humans. We have been studying bacteria for many years in the science field, and many studies exist today that center around these organisms. Understanding how one cell can function as a living organism is important to us because we are made up of a lot of cells together, and only count ourselves as one living thing altogether. Bacteria are also very important to the pharmaceutical industry and to all humans in general, due to their appearance in some drugs. Bacteria also have a few symbiotic relationships to us, such as the E. coli in our gut, which is not the harmful strain, but the kind that makes vitamin K for our bodies because we cannot make it ourselves. On a cellular level, humans are comprised of a higher percentage of bacterial cells than eukaryotic ones, which shows just how important bacteria is for sustaining life. Bacteria come in many shapes and classifications, and represent a very diverse group of organisms by performing a multitude of functions. The video below describes some of the variations of bacteria known today. media type="custom" key="24116346" Different Bacteria Types

<span style="font-family: Arial,Helvetica,sans-serif;">One other very significant part of bacteria is how quickly they can replicate and create colonies. Each bacterial cell can reproduce by replicating its DNA loop, then splitting in half. The following video describes how quickly the bacteria can increase in number. <span style="font-family: Arial,Helvetica,sans-serif;">media type="custom" key="24116356" <span style="font-family: Arial,Helvetica,sans-serif;">Bacteria Replication

<span style="font-family: Arial,Helvetica,sans-serif;">The cell structure of many bacteria are similar. The diagram in figure 3 shows the multiple different parts of the bacterial cell.

<span style="font-family: Arial,Helvetica,sans-serif;">Figure 3: Bacterial cell parts and structure. The blue mass is the circular loop of DNA, called the nucleoid. Shown in green are the bacteria's ribosomes, the only organelle in the cytosol. The cell moves via rotation of the flagella, shown in brown. The cytoplasmic membrane holds the cytosol in the cell, the cell wall gives the bacteria shape, and the capsule protects the cell from external stresses. The yellow strand-like structures are known as pili, and are used for surface adhesion. ( <span style="font-family: Arial,Helvetica,sans-serif;">[] <span style="font-family: Arial,Helvetica,sans-serif;">)

<span style="font-family: Arial,Helvetica,sans-serif;">Bacterial diversity aids in the multitude of functions that can be determined for the domain. Three research groups studied bacteria in extremely different situations: <span style="font-family: Arial,Helvetica,sans-serif;">This paper, written in 2013, was on the microbes of soil and how they reacted to global changes such as mowing, adding nitrogen, adding phosphorous, adding water, heating, etc. The paper observes that the abundance of almost all genes were sensitive to the addition of nitrogen, which is found in most fertilizers. (3) <span style="font-family: Arial,Helvetica,sans-serif;">In this paper, bacteria are tested with green fluorescent proteins (GFP’s). This will be beneficial for testing for diseases in other organisms. A few variants of GFP’s were tested on a few different bacterial strains to find the optimum variant protein to label the bacteria. (2) <span style="font-family: Arial,Helvetica,sans-serif;">Yet another paper is a review on biohydrogen, which is thought to be a potential future fuel. Some bacteria can produce hydrogen from water, solar energy, and some organic substrates, and these were reviewed as having already been studied in the search for ways to make biohydrogen a working fuel. Two issues the paper notices with this endeavor are high production costs for disappointingly low yields. (1)
 * <span style="font-family: Arial,Helvetica,sans-serif;">Response of the Abundance of Key Soil Microbial Nitrogen-​cycling Genes to Multi-​factorial Global Changes **
 * <span style="font-family: Arial,Helvetica,sans-serif;">Benchmarking Various Green Fluorescent Protein Variants in Bacillus Subtilis, Streptococcus Pneumoniae, and Lactococcus Lactis for Live Cell Imaging **
 * <span style="font-family: Arial,Helvetica,sans-serif;">Trends in biohydrogen production: major challenges and state-​of-​the-​art developments **

<span style="font-family: Arial,Helvetica,sans-serif;">Not only do these three studies show the diversity that bacteria has accomplished, but food does as well. Lactobacillis bacteria are found in sourdough bread and yogurt, lending its tangy taste to the foods. As far as how the bacteria eat, there are three groups:
 * <span style="font-family: Arial,Helvetica,sans-serif;">Phototrophs - cells contain thylakoids and can harvest solar energy from sunlight to fuel cellular processes
 * <span style="font-family: Arial,Helvetica,sans-serif;">Organotrophs - bacteria that eat living things
 * <span style="font-family: Arial,Helvetica,sans-serif;">Lithotrophs - bacteria that eat nonliving things

Bacteria also have the ability to protect themselves by making spores. These endospores can withstand extreme temperatures and toxic chemicals. The bacteria can reestablish itself from the spore once the stresses have been alleviated.

Finally, bacteria can communicate with each other via quoram sensing. This process is for regulation, and is described in the following video. media type="custom" key="24283182" Quoram Sensing

References: <span style="font-family: 'Times New Roman',serif;">1) Kumar Gupta, Sanjay, Et. Al. "Trends in Biohydrogen Production: Major Challenges and State-​of-​the-​art Developments." //Environmental Technology// 34.13-14 (2013): 1653-670. //Scifinder Scholar//. Web. 10 Oct. 2013. <span style="font-family: 'Times New Roman',serif;">2) Overkamp, Wout, Et. Al. "Benchmarking Various Green Fluorescent Protein Variants in Bacillus Subtilis, Streptococcus Pneumoniae, and Lactococcus Lactis for Live Cell Imaging." //Applied and Environmental Microbiology// 79.20 (2013): 6481-490.//Scifinder Scholar//. Web. 10 Oct. 2013. <span style="font-family: 'Times New Roman',serif;">3) Zhang, Ximei, Et. Al. "Response of the Abundance of Key Soil Microbial Nitrogen-​cycling Genes to Multi-​factorial Global Changes." //PLoS One// 8.10 (2013): n. //Scifinder Scholar//. Web. 10 Oct. 2013.