Microbe Murder Mystery

Microbes in the Environment Microbes can be isolated from all sections of the biosphere Each species of microbe has certain requirements for growth and survival such as pH, temperature and nutrients Therefore, some species can be uniquely linked to specific areas. Forensic scientists use this analytical capability to help lay out certain crime scene scenarios.

Diatoms Diatoms are protists in the Phylum Chrysophyta (golden brown algae) They are single celled eukaryotes found in fresh, marine, or brackish water. They can be suspended (planktonic) or attached and living on the bottom (benthic).

Diatom Characteristics Diatoms have a rigid two-piece cell wall composed of silica. These walls are called frustules. Nicknamed “glass boxes” The frustules are extremely resistant to decay and therefore remain long after the cytoplasm is dead Their numbers fluctuate with the seasons, reaching peak levels in the spring and fall.

Diatoms and Drowning Diatoms have been useful in the diagnosis of death by drowning. When diatom-laden water is inhaled during drowning, some diatoms will enter the circulatory system and be carried by the blood to various internal organs. Lungs and soft tissue organs can be digested using acid and the hard frustules remain.

Diatoms and Drowning More recently, bone marrow samples are used. Diatoms can enter the lungs postmortem through the involuntary transfer of contaminated water. So their presence in these organs does not definitely tell us if death occurred by drowning or injury Therefore, it is more conclusive when found in bone marrow because it could only get there if inhaled while drowning. The diatoms must be found in both the bone marrow and the liquid in which the victim died. It is more accurate in fresh water than salt water

Diatoms in this Lab Some important diatoms in this lab activity include: Micrasterias Synedra

Other Microbes Protozoa are animal-like protists. This means they must find food and eat it. Included in this group are: Paramecium Blepharisma Bursaria Vorticella Euplotes

Other Microbes Algae are plant-like protists. This means they can make their own food by photosynthesis. Included in this group are: Volvox Anabaena

The Crime Scenario The city councilman was found floating facedown in the middle of his swimming pool by a neighbor whose sleep had been disturbed by a loud splash.

The Crime Scenario The autopsy revealed hemorrhage into the right sterno-mastoid muscle; fracture of right hyoid bone; and recent bruising involving the tip of the tongue (all signs of a struggle and possible strangulation) Bilateral pulmonary edema and 300ml of a water fluid found in the stomach. Nitric acid extract of femoral bone marrow revealed the presence of a distinctive species of frustule.

Possible Explanations Accidentally tripped and fell into his own swimming pool (there was an over-turned deck chair at the pool’s edge) Intentionally drowned in the swimming pool by an unknown assailant (there were internal injuries) Intentionally drowned somewhere else and his body was thrown into the swimming pool by the murderer to avert attention from the real murder site

Forensic Assignment You---a microbiologist from a nearby university are to assist the Coroner’s Office in this investigation. There are three outdoor areas frequented by the victim: White River, Prairie Creek Reservoir, and Duck Pond You must match samples taken from each location plus the swimming pool to fluid samples extracted from the body.

Forensic Ruling What was the manner of death? (natural, accident, suicide, homicide, undetermined, and pending). Where did the councilman die? How did the councilman die? What was the sequence of events which culminated in the councilman’s death?