Title page for ETD etd-06172010-112221


Type of Document Master's Thesis
Author Tydings, Heather Anne
URN etd-06172010-112221
Title Identification and Optimization of the Antagonistic Potential of Native Spinach Microbiota towards Escherichia coli O157:H7
Degree Master of Science
Department Food Science and Technology
Advisory Committee
Advisor Name Title
Ponder, Monica A. Committee Chair
Boyer, Renee R. Committee Member
Falkinham, Joseph O. III Committee Member
Keywords
  • epiphytic bacteria
  • spinach
  • microbial diversity
  • bacterial interaction
Date of Defense 2010-06-03
Availability restricted
Abstract
Leafy greens such as spinach have been the object of several recent food-borne pathogen outbreaks. The purpose of this study was to isolate bacteria spinach epiphytic bacteria that inhibit growth of E. coli O157:H7, which we describe as antagonism. The mechanism of antagonism was investigated and we attempted to improve the antagonistic potential in vitro and on spinach leaves when cellobiose, a carbon source utilized by the antagonists but not E. coli O157:H7, was added.

There were larger culturable populations of bacteria on the leaves of savoyed cultivars compared to flat. From the isolated colonies, 47 displayed antagonism towards E.coli O157:H7, and were identified as members of 11 different genera and sixteen species. A representative isolate from each species was evaluated for three possible mechanisms of antagonism: acid production, secretion of an inhibitory compounds or secreted protease. The majority (14/16) produced at least a moderate level of acid. Two of these strains, Paenibacillus polymyxa and Pseudomonas espejiana, were found to secrete a non- protease antagonistic compound.

These antagonists varied in their reduction of E.coli O157:H7 numbers in vitro, but all significantly reduced numbers in 48 hours of co-culturing in nutrient rich media. Five antagonists resulted in a significant reduction in E.coli O157:H7 populations when co-cultured on spinach leaves. Application of cellobiose did not improve the amount of antagonism in vitro or on the leaf surface after 24 hours.

Files
  Filename       Size       Approximate Download Time (Hours:Minutes:Seconds) 
 
 28.8 Modem   56K Modem   ISDN (64 Kb)   ISDN (128 Kb)   Higher-speed Access 
[VT] Tydings_HA_T_2010.pdf 1.80 Mb 00:08:21 00:04:17 00:03:45 00:01:52 00:00:09
[VT] indicates that a file or directory is accessible from the Virginia Tech campus network only.

Browse All Available ETDs by ( Author | Department )

dla home
etds imagebase journals news ereserve special collections
virgnia tech home contact dla university libraries

If you have questions or technical problems, please Contact DLA.