| Survey
of Extracellular Products of Biofilm Bacteria
Adrienne
Yanez
Notre
Dame
Summer
Mentor: Dr James Maki
Dreissena
polymorpha (the zebra mussel) is a biofouling invertebrate introduced
into North American inland waters. The D. polymorpha life cycle
involves metamorphosis from a planktonic larval stage to a benthic adult
stage. This metamorphosis is initiated when D. polymorpha detects
environmental cues indicating the presence of a suitable substratum on
which to settle. Glycoproteinaceous threads are then secreted from the
byssal gland and these attach the mussel to the substratum. Adult D.
polymorpha are able to cut their byssal threads, move to a new location
and resecrete threads to reattach.
Microbial
biofilms consist of matrix enclosed microorganisms attached to each other
and/or surfaces or interfaces. Natural biofilms consisting of multiple
species of microorganisms have been shown to induce D. polymorpha
settlement on polycarbonate surfaces but not on glass (Kavouras & Maki
2003). Single species bacterial films have been reported to influence (stimulate
or inhibit) settlement of marine invertebrates (Wieczorek & Todd 1998,
Maki 1999, Huang & Hadfield 2003), including the inhibition of reattachment
of D. polymorpha (Kavouras and Maki 2004). Kavouras and Maki (2004)
found 7 out of 10 strains of biofilm bacteria isolated from natural biofilm
to be inhibitory to zebra mussel reattachment on polystyrene but not on
glass. Further, cell-free bacterial extracellular products from 2 of 3
inhibitory strains reduced reattachment of D. polymorpha on polystyrene
but not on glass (Kavouras & Maki 2004). The exact mechanism(s) of
inhibition are unknown.
Because
the data suggested that bacterially produced extracelluar products could
inhibit D. polymorpha reattachment, the objective of this project
was to characterize biofilm isolates based on extracellular activity to
detect any trends that may exist among inhibitory versus non-inhibitory
strains. Twenty one strains of bacteria previously isolated from natural
biofilm were tested for antibiotic production and resistance as well as
extracellular degradation of amylase, casein, lipase, chitin, and phenanthrene.
Two of the strains (JK001 and JK021) were reported to be inhibitory to
D.
polymorpha reattachment on polystyrene, one (JK005) was reported to
be non-inhibitory on polystyrene while the rest have unknown effects on
D. polymorpha reattachment.
Twelve
of the strains tested were amylolytic, 14 were lipolytic, thirteen were
proteolytic, two were antibiotic producing, three were antibiotic resistant
and one was chitinolytic. Strains JK001 and JK021, inhibitory to zebra
mussels, were both amylolytic and proteolytic. Strain JK021 was additionally
lipolytic while non-inhibitory strain JK005 was also amylolytic, proteolytic
and lipolytic. There was no consistent relationship regarding the extracellular
activity and the inhibition of D. polymorpha reattachment. However,
it is likely that although the extracellular enzymes produced by the different
bacteria all provide the same general type of activity, they are not identical.
This difference may play a role in whether or not they have an effect on
D.
polymorpha reattachment. Identification of bacteria for phylogenetic
analysis will provide insight into relationships between and among inhibitory
and non-inhibitory bacteria.
Characterization
of the compositional difference of extracellular products when the bacteria
are on polystyrene versus glass is needed to better understand the interactions
between the substratum and the bacteria. |
