Biol. Mar. Mediterr. (2012), 19 (1): 238-239
M. Papale, M. Borghini1, A. Ribotti2, A. Lo Giudice, L. Michaud,
R. Sorgente2, M. De Domenico, E. De Domenico
Dip. Biologia Animale ed Ecologia Marina, Università di Messina, Salita Sperone, 31 - Messina, Italia.
[email protected]
1
Istituto di Scienze Marine (ISMAR-CNR) - Pozzuolo di Lerici (SP), Italia.
2
Istituto per l’Ambiente Marino Costiero (IAMC-CNR), Loc. Sa Mardini - Torregrande (OR), Italia.
LUMINESCENT BACTERIA AND WATER MASSES RELATIONSHIPS
ALONG A SECTION BALEARIC ISLANDS - SARDINIA
RELAZIONI TRA BATTERI LUMINOSI E MASSE D’ACQUA
LUNGO UN TRANSETTO ISOLE BALEARI - SARDEGNA
Abstract - In order to evaluate quantitative and qualitative luminescent bacteria distribution, 101
seawater samples from 5 stations along a section Balearic Islands - Sardinia (Western Mediterranean
Sea) were analysed during January 2012 and compared with data from May 2010. Luminescent bacteria
plate counts showed a patchiness distribution that increases in the intermediate layer and at its interface
with Deep Waters. An ARDRA analysis on isolated strains was carried out to evaluate the microbial
diversity of the luminous communities and one selected representative for each ARDRA group was
identified via the 16S rDNA sequencing.
Key-words: bacteria, luminous organisms, distribution, water masses.
Introduction - A wide literature on the systematic, metabolic features, biochemical
pathways and ecology of luminous bacteria (LB) is available, but their distribution
and role in marine environment are not completely known (Gentile et al., 2009;
Ruggeri et al., 2010). De Luca et al. (2009) found higher values in surface waters
(0-200 m) of the western Mediterranean Sea than at 800-1200 m depth in the
other Mediterranean surveyed areas. In May 2010 quantitative and qualitative LB
distribution was evaluated along a section Balearic Islands - Sardinia (Michaud et
al., 2011), then repeated in January 2012. The circulation in the area, characterized
by the typical 3-layers system with a geostrophical path for intermediate waters, is
often influenced by mesoscale eddies coming from the Algerian basin and interacting
with surface and intermediate waters (Puillat et al., 2002), transporting intermediate
and modified Atlantic waters through the Algerian area.
Materials and methods - From 11 to 27 January 2012 the multidisciplinary cruise
ICHNUSSA2012 was carried out on board the R/V Urania (CNR) between Menorca
(Balearic Islands) and Sardinia. A total of 101 seawater samples from 5 stations were
collected, from surface to 10 m above the bottom, by a Rosette sampler equipped with
12L Niskin bottles. A CTD probe 911plus SeaBird was employed for conductivity,
temperature, pressure, dissolved oxygen and fluorescence measurements. LB were
counted on Millipore filters (0.45 µm) placed on Sea Water Complete (SWC) agar
plates. Counts from various filtered volumes and duplicate plates were normalized to
100 mL. LB were then isolated from the same plates and clustered by the Amplified
rDNA Restriction Analysis (ARDRA). Representative isolates were identified by the
16S rRNA gene sequencing. The bacterial community structure was determined by
Automated Ribosomal Intergenic Spacer Analysis (ARISA) (Danovaro et al., 2006).
Results - Along the section, LB were detected in about 30% of samples with
abundance values that ranged from 0 to 15 CFU 100mL-1. LB plate counts showed
a patchiness distribution increasing in the intermediate layer (LIW) and at its
interface with Deep Waters. Highest counts (15 CFU 100 mL-1) were found at 1250
Luminescent bacteria and water masses relationships along a section Balearic Islands - Sardinia
239
and 1000 m depths (Stations S04 and S08, respectively) along the Balearic side of the
section. With respect to the hydrodynamics, the eastern side was characterized by
the presence of the LIW moving northward along the Sardinian slope with its core
at about 500 m depth (salinity of about 38.65 psu and temperature of 13.75 °C). It
was visible until about 100 km from the coast. On the western Balearic side LIW
was not visible, probably due to the distance of the first station of the transect (S02)
from the Balearic slope. Below new deep waters (Schroeder et al., 2009), originated
in the Gulf of Lion, occupied the area from about 2000 m depth to the bottom and
were characterized by dissolved oxygen of about 4.5 mL L-1.
Conclusions - Bacterial genotypes detected by ARISA formed five clusters that
mainly grouped per water mass (E: Epipelagic; M: Mesopelagic; B: Bathypelagic layers)
rather than per station. A total of 43 luminescent strains were isolated. Such strains
were clustered into 4 OTUs and one isolate per OTU was identified at molecular
level. OTUs 1 and 2 (46.5 and 23.3% of total isolates, respectively) resulted closely
related to two Gram-negative bioluminescent bacteria: Photobacterium phosphoreum
(99% homology) and P. halotolerans (97% homology). OTU 3 (11.6%) was related to
the Gram-negative, bioluminescent, rod-shaped, motile, facultatively anaerobic and
halophilic Vibrio harveyi (98% homology). Finally, the OTU 4 (18.6%) was related to
Vibrio (Aliivibrio) fischeri (98% homology). Such bacteria are normally found in all
marine environments and they are key research organisms for the bioluminescence
and symbiosis studies.
Acknowledgements: A special thank to Capt. Emanuele Gentile (R/V Urania), its crew and technicians
onboard.
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This work is funded by: Messina Univ (PRA 2005); EU IP-MyOcean project (contract FP7SPACE-2007-1 n. 218812).