Saturday, September 24, 2016

Loving microbes

I thought I would write a post for all the non-microbiologists that might be wondering what microbes are in our logo and why.
Before that though, maybe I need to mention that there are a small number of bacterial basic shapes and the rest are just types of those basic shapes. Bacilli are rods, cocci are spheres, spirochetes are spirals, filamentous bacteria form long filaments that look like fungi, and pleomorphic are weirdos that don't adhere to one shape. In general (except for pleomorphic) when a bacterium is healthy and it divides, the two resulting bacteria look exactly the same shape (rod to rod).

Okay, so here is a vector version of the linocut logo I made:

So what are they?
 #1: A general bacterial shape called a vibrio which is just a curved rod. (The straight version is called a rod or a bacillus). An example of bacteria with this shape is Vibrio cholerae the causative agent of cholera.

#2: This is a chain of the bacterial shape called cocci. The kind of cocci that form a chain like this are from the genera Streptococcus, Lactococcus, and Enterococcus. Lactococcus and Enterococcus were classed as Streptococcus until 1984 and they are difficult to distinguish from streptococci by morphology alone (shape). All 3 genera are found living in and on humans. Most are either beneficial or neutral, while some can be pathogens. (Genera is the plural form of the word genus, and is the classification level above species - wikipedia explanation here - scroll down to Modern system of classification for a good graphical explanation).

#3: This is a bunch or cluster of cocci and the kind of cocci that form this shape are from the genus Staphylococcus. Staph are also found living on and inside of humans and some are neutral and some are pathogens. The most famous of the pathogens at the moment is Staphylococcus aureus because it is increasingly methicillin resistant (MRSA) making it very difficult to treat.

#4: This is my poor representation of a spirochete or a really twisted vibrio. I didn't have any particular bacteria in mind for this shape but well known spirochetes are the Treponema which cause syphilis and the Borrelia which cause Lyme disease.

#5: This is a bacilli with fimbriae which is common among Escherichia coli that cause urinary infections. The hairy-like fimbriae help the bacteria to attach to the host cells.

#6: 6a and 6b are different serotypes of the same species of bacteria. Streptococcus pneumoniae (or the pneumococcus) exists as diplococci (doublets) instead of chains like other streptococci. It can have a sugar capsule (b) to protect it from the immune system or not (a). Pneumococci without capsules are generally not pathogenic. Pneumococcus lives in humans mouth, throat, and nasopharynx and can sometimes cause disease. I included both forms because I have studied the pneumococcus for many years and it is a bacterium near and dear to me.

#7: This is a bacilli with flagella. A flagellum is larger and longer than fimbriae or pili and is used for movement rather than attachment. Pseudomonas is a genera of bacilli bacteria that have flagella. Another famous bacteria that has flagella is Helicobacter pylori - generally H. pylori are considered vibrio (curved rod) but in some pictures the curvature looks small and it looks like a normal bacillus).

#8: Neisseriae or coffee-bean shape in pairs is also another cocci bacteria. This shape is particular to the genus Neisseria. There are 11 species of Neisseria that colonize (live in/on) humans and only 2 are pathogens. They are Neisseria meningitidis (causes meningitis) and Neisseria gonorrhoeae (causes gonorrhoea).

#9: Similar to #7 but I was specifically thinking of Salmonella and more specifically Salmonella enterica. Various strains cause typhoid fever or food poisoning.

#10: Depending on my artistic skills and your interpretation these can either be tennis racket or drumstick shape common to Clostridium tetani, the causative agent of tetanus, or the clubbed rods of Corynebacterium diphtheria which cause diphtheria.

Some of the shapes I played with the sizes - so these sizes are not to scale! For example, the staph, strep, and pneumos should all be about the same size but the pneumos look much bigger here. I included shapes I either thought were interesting, or important bacteria, or bacteria that I am personally interested in (like streptococci). One major bacteria I didn't include is the basic bacillus shape common to Bacillus anthracis (anthrax) and Mycobacterium tuberculosis. It just didn't look good to me so it was omitted.

And there you have it- a crash course on bacterial shapes.

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