#### Title

Effect of Increasing the Complexity of a Network on the Accuracy of Physarum polycephalum to a Minimum Steiner Tree

#### School Name

Spring Valley High School

#### Grade Level

10th Grade

#### Presentation Topic

Mathematics

#### Presentation Type

Non-Mentored

#### Abstract

Studies on the brainless slime mold Physarum polycephalum have shown that it is able to condense into very efficient networks. However, the closeness of its networks to the shortest possible length of the total network, also known as a Steiner tree, has not been found. This research sought to find out how accurate the P. polycephalum's length would be to a Steiner tree's minimum length as the complexity of the system was changed. The networks presented to the slime mold were 4-node, 5-node, 6-node, and 8-node. P. polycephalum was subcultured onto Petri dishes containing 2% non-nutrient agar. Each group was provided with a designated network of oat flakes with a calculated minimum Steiner distance. It was hypothesized that P. polycephalum would be closest to the 4-node network, given that it is the simplest system to perform chemotaxis in. The total length spanned by each organism was measured and compared to the minimum possible distance. However, little growth occurred in the P. polycephalum, so data is inconclusive. The absence of growth is likely due to errors in controlling an ideal environment for P. polycephalum, or from subculturing the plates using a plasmodium that had not grown enough. It is also possible that harmful microbes entered some Petri dishes via oat flakes that were improperly kept sterile. This experimental procedure would be improved by letting the stock plasmodium grow out fully and also ensuring that the oat flakes are out of the packaging for as little time as possible.

#### Recommended Citation

Fletcher, Wesley, "Effect of Increasing the Complexity of a Network on the Accuracy of Physarum polycephalum to a Minimum Steiner Tree" (2020). *South Carolina Junior Academy of Science*. 6.

https://scholarexchange.furman.edu/scjas/2020/all/6

#### Location

Furman Hall 121

#### Start Date

3-28-2020 11:15 AM

#### Presentation Format

Oral and Written

#### Group Project

No

Effect of Increasing the Complexity of a Network on the Accuracy of Physarum polycephalum to a Minimum Steiner Tree

Furman Hall 121

Studies on the brainless slime mold Physarum polycephalum have shown that it is able to condense into very efficient networks. However, the closeness of its networks to the shortest possible length of the total network, also known as a Steiner tree, has not been found. This research sought to find out how accurate the P. polycephalum's length would be to a Steiner tree's minimum length as the complexity of the system was changed. The networks presented to the slime mold were 4-node, 5-node, 6-node, and 8-node. P. polycephalum was subcultured onto Petri dishes containing 2% non-nutrient agar. Each group was provided with a designated network of oat flakes with a calculated minimum Steiner distance. It was hypothesized that P. polycephalum would be closest to the 4-node network, given that it is the simplest system to perform chemotaxis in. The total length spanned by each organism was measured and compared to the minimum possible distance. However, little growth occurred in the P. polycephalum, so data is inconclusive. The absence of growth is likely due to errors in controlling an ideal environment for P. polycephalum, or from subculturing the plates using a plasmodium that had not grown enough. It is also possible that harmful microbes entered some Petri dishes via oat flakes that were improperly kept sterile. This experimental procedure would be improved by letting the stock plasmodium grow out fully and also ensuring that the oat flakes are out of the packaging for as little time as possible.