The Hawaiian Bobtail Squid (Euprymna scolopes) is
characteristic in its association with the bioluminescent bacterium Vibrio
fischeri and is a model organism for host-bacterial
associations. There are however more associations of bacteria within the squid
then vibrio fischeri alone.
Recent studies of this organism have revealed a second association of
bacteria in the reproductive organ, the accessory nidamental gland (ANG) of
female Squid. This consortium is dominated by the clade Rhodobacteracea (roseobacter)
(Collins et al, 2012, 2015), which is known to contain
antimicrobial properties in free-living bacteria cultures. Although cultures in
associations to test the antimicrobial property of the bacteria had not been
undertaken.
The Bacterium are held within epithelium tubules in the accessory
nidamental gland which connects to the nidamental gland that secretes a jelly
coat surrounding the fertilized eggs of the squid.
E. scolopes has a cool trick to protect its eggs from damage when
laid in the environment away from the protection of the parent where predation,
pathogens and fouling are all risks. Bacteria are secreted onto the Jelly Coat
of the egg from the ANG before being laid in the environment. These bacteria
contain antimicrobial properties to prevent fouling of the eggs.
Gromek et al, (2016) characterize the genome and
secondary metabolites of a new strain of roseobacter bacteria, isolated from
the Jelly coat of E. scolopes eggs (JC1).
In the study, they obtain Hawaiian bobtail squids from the sand flats in
Oahu Hawaii. Once in captivity eggs were flash frozen on the 11th day of
development from one female individual. 10 eggs are thawed and the embryos are
removed. The jelly coats where isolated and sterilized. The bacteria were
isolated and cultured, the genome was sequenced and analysed using MasterPure
DNA Purification kit.
Using taxonomic analysis of the 16s rRNA sequence they indicated
the strain JC1 belonged to the Leisingera genus. They
then go on to confirm the presence of indigoidine (which has
antimicrobial properties) by mass spectroscopy in this strain. In a
co-culture with 5 species within the Vibrionaceae family,
the zone of inhibition around JC1 was shown to be significant
around V. fischeri, P. leiognathi, V. parahaemolyticus, V.
anguillarum, and V. harveyi.
It indicates that this new strain may be the active
antimicrobial action in the defence against the eggs in Hawaiian bobtail
squid.
Inhibition of representatives of the Vibrio genus may
lead to interesting results in the inhibition of Vibrio
cholorea, which may be an interesting direction to take the research.
References
Collins, A. J., Fullmer, M. S., Gogarten, J. P.,
& Nyholm, S. V. (2015). Comparative genomics of Roseobacter clade bacteria
isolated from the accessory nidamental gland of Euprymna scolopes. Frontiers
in microbiology, 6, 123.
Collins, A. J., LaBarre, B. A., Wong Won, B. S.,
Shah, M. V., Heng, S., Choudhury, M. H., … Nyholm, S. V. (2012). Diversity and
Partitioning of Bacterial Populations within the Accessory Nidamental Gland of
the Squid Euprymna scolopes. Applied and Environmental Microbiology, 78(12),
4200–4208. http://doi.org/10.1128/AEM.07437-11
Article Reviewed
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Gromek, S. M., Suria, A. M., Fullmer, M. S.,
Garcia, J. L., Gogarten, J. P., Nyholm, S. V., & Balunas, M. J.
(2016). Leisingera sp. JC1, a Bacterial Isolate from Hawaiian
Bobtail Squid Eggs, Produces Indigoidine and Differentially Inhibits
Vibrios. Frontiers in Microbiology, 7, 1342.
http://doi.org/10.3389/fmicb.2016.01342
I always find it fascinating to learn about how different organisms rely so heavily upon mutualisms with associated microbes for healthy development and functioning. It's almost as if JC1 provide a form of parental care, keeping the eggs healthy and allowing the female squid to invest energy elsewhere - evolution can be pretty neat! Did the authors discuss the potential functions of JC1 inhibiting Vibrio fischeri in much detail? This is an interesting result given that the bobtail squid's most iconic symbiosis is with V. fischeri.
ReplyDeleteAdditionally, I really like your idea for potential research into inhibition of Vibrio cholerae. As i mentioned in my blog post entitled 'Microplastics as a Novel Mode of Transportation for Potentially Dangerous ‘Hitchhiking’ Vibrio Spp.', the incidence of Vibrio infection in humans in increasing with rising sea surface temperatures, so research into this area could be really important.