Antibacterial activity in the sea urchin Echinus esculentus

Unkles, Shiela E (1976) Antibacterial activity in the sea urchin Echinus esculentus. MSc(R) thesis, University of Glasgow.

Abstract

The studies described in this thesis fall into two parts: 1. A survey of the normal bacterial flora of the common British sea urchin, Echinus esculentus, in comparison with the bacterial flora of seawater and sand from the same locality. 2. An investigation of the antibacterial activity in E. esculentus. This formed the main part of the work. In part 1, the normal bacterial flora, of the sea urchin was examined with isolates from the coelomic fluid, the peristomial membrane and the gut. Aerobic heterotrophic organisms from these sites were identified by a scheme based on that of Shewan, Hobbs and Hodgkiss (1960). The main genera identified were PseudomonasVibrio, Aeromonas, Flavobacterium, Acinetobacter and Moraxella. A few Gram-positive bacteria were also isolated. Of 188 urchins examined, two-thirds had sterile coelomic fluid and it is likely that organisms found there had been introduced by damage to the animal and do not form a permanent indigenous flora. In part 2, initial experiments showed that urchins were capable of clearing, within 24 h, large doses of marine bacteria which had been injected into the coelomic cavity. This indicated that sea urchins possess an efficient antibacterial mechanism. A procedure was developed to examine in vitro the coelomic fluid of sea urchins for antibacterial activity. As test bacterium in these experiments a marine pseudomonad, strain 111, was chosen bacause it produced characteristic black, agar-digesting colonies on marine 2216E agar which were not readily confused with contaminating bacteria. A non-bactericidal control fluid was included in all tests. This consisted of the boiled supernatant of coelomic fluid which was considered to be nutritionally and ionically equivalent to coelomic fluid, and which allowed growth of the test bacterium. Strain 111 incubated in coelomic fluid for 48 h WS'S usually reduced to less than 5% of its initial viable count, whereas in the control fluid the bacteria multiplied. Coelomocytes clot almost immediately when coelomic fluid is withdrawn from urchins but this appeared to have no effect on in vitro antibacterial activity. In vitro the fluid from all 188 urchins studied showed antibacterial activity. The activity was temperature-dependent (optimum 4

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Additional Information: Adviser: A C Wardlaw
• Keywords: Microbiology
• Date of Award: 1976
• Depositing User: Enlighten Team
• Unique ID: glathesis:1976-72951
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 11 Jun 2019 11:06
• Last Modified: 11 Jun 2019 11:06
• URI: https://theses.gla.ac.uk/id/eprint/72951