20th October 2016 Microbiology Gram-Positive Anaerobic Spore-forming Rods Phylogenetic Tree Gram-positive bacteria are apart of the family bactericaeae, and stems from the last common ancestor (LUCA). Gram-positive bacteria are divided into Actinobacteria, Firmicutes and Mollicutes. Clostrida belong to Firmicutes. Proteobacteria is gram-negative bacteria. The bacteria phylogenetic tree is based on the 16S rRNA sequencing. Defining Characteristics of Clostridia Clostridia are obligate anaerobes; they cannot grow in oxygen environment. This is because they do not have the enzymes to deal with the oxygen in the environment. Oxygen can be very dangerous as it is a very reactive oxidative species. Because of their need for no oxygen, Clostridia mainly live in the soil and water. It doesn't take much depth in the soil to reach limiting to no oxygen. They are gram-positive (more peptidoglycan on the cell wall), sporulaiting rods. Clostridia sporulate with either terminal (lolly pops) or subterminal spores, which distend the sporangium (look swollen at the end). Clostridia produce neurotoxins, which affected and have activity in the nervous system, mainly the synapses. There are different types of neurotoxins released; this divides Clostridia into different categories depending on which neurotoxin they release: - A - B - C1 - D - E - F - G Clostridia generally release one toxin type, however they can release two, one being its major toxin and the other its minor e.g. Af (produces mainly A (as major toxin) but can produce F (as its minor toxin)), Ba and Ab. There are mosaic variants of the neurotoxins, and they occur between C and D. Within CD there is C-D, D and D-C. Therefore, a mosaic variant is the first part of C and the second part of D is C-D, and then if you have the first part of D and the second part of C it is D-C. There is a swap over and a 50-50 split.
Microbiology 20th October 2016 Clostridia become very difficult to treat when it sporulates, as they are resistant to extremes. Historical Perspective of Clostridium botulinum Emperor Leo VI (886-912) - Macedonian ruler who banned the eating of blood sausage. Blood sausage was thought to have potential to become and anaerobic environment, great for C.botulinum. It was seen that people were dying from eating it. 1895 Van Ermengen - Home cured Ham outbreak - managed to isolate C.botulinum Bacillus botulinus - botulus means "sausage". However, Bacillus was found to be an aerobe; it was Clostridia, so it was later classified as Clostridium (anaerobe). Physiology There are four groups based on proteolysis - proteolytic, it will break down protein in food; giving it a slimy, gone off appearance; spoils the food. Properties Toxin Types A, B, F B, E, F C. D G Proteolysis + - Saccharolysis - + Disease host food. Group I human Group II human Group III weak - I animal Group IV Within in the groups there are the types of Clostridia that predominate that group e.g. group I has type A,B, and F. Saccharolysis is