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mater in the water and the proliferation of bacteria, reaching values up to 10
4
CFU
Artemia
-1
,
and that
Vibrio
is the predominant group among culturable bacteria, while
V. alginolyticus
was the dominant species (Olsen
et al.
2000; Villamil
et al.
2003).
In a recent study, Høj
et al.
(2009) analysed the localization, abundance and community
structure of bacteria associated with
Artemia
nauplii. Most bacteria were localized in the
nauplii gut, with external surfaces having limited bacterial colonization. Enrichment with
microalgae or with commercial lipid emulsions for 24 h generally increased the bacterial load
of newly hatched nauplii from 10
1
to 10
2
-10
6
CFU
Artemia
-1
and in some cases, the enrich-
ment process shifted the bacterial community towards
Vibrio
spp. Strains isolated from newly
hatched nauplii belonged to the genera
Sphingonomonas
,
Rhizobium
,
Pseudomonas
and
Bre-
vundimonas
and also several
Micrococcus
spp. were isolated.
Pseudomonas
and
Vibrio
spp.
were predominant in enriched nauplii.
V. alginolyticus
was the dominant species among the
Vibrio
isolated in all treatments. DGGE profiles confirmed that the bacterial community was
composed of populations related to members of γ-Proteobacteria and also members of the
Planctomycetales phylum. In nauplii enriched with algae, a phylotype identified as
Antarto-
bacter
sp., from the
Roseobacter
supercluster, was detected.
Strains of
Vibrio proteolyticus
,
Pseudomonas fluorescens
and
V. alginoliticus
have been
demonstrated to have a negative effect on
Artemia
cultures (Verschuere
et al.
1999) and can
be potentially detrimental to fish larvae.
16.2.4 Copepods
Copepods continuously ingest particles of organic matter and produce faecal pellets, incorpo-
rating and releasing bacteria to the surrounding medium and acting as a 'microbial hotspot' in
the sea (Tang 2005). Copepods have bacteria attached to their external surface (Carman and
Dobbs 1997; Brandt
et al.
2010), predominantly near the mouth and the anus and between
the segments (Carman and Dobbs 1997), and in their intestine and faecal pellets (Hansen
and Bech 1996). The numbers of culturable bacteria in cultured copepods are generally lower
than in
Artemia
, ranging in values from 10
2
to 10
4
CFU copepod
-1
(Hansen and Bech 1996;
Verner-Jeffreys
et al.
2003; Tang
et al.
2009). The bacterial community composition of cope-
pods is influenced by the food and copepod life history (Tang
et al.
2009). The main species of
culturable bacteria associated with marine copepods belong to the
Vibrio
,
Pseudomonas
and
Cytophaga
genera (Sochard
et al.
1979). Copepod faecal pellets promote the development of
bacteria which differ from the surrounding water, with predominant species belonging to the
genera
Bacillus
,
Cytophaga
,
Pseudomonas
and
Vibrio
in
Acartia tonsa
(Delille and Razouls
1994; Hansen and Bech 1996). Recently, culture-independent methods revealed a prevalence
of α-Proteobacteria and also δ-Proteobacteria and Bacteroidetes on copepods (Møller
et al.
2007; Tang
et al.
2009). Using different grinding procedures, Brandt
et al.
(2010) compared
surface-attached bacteria and total (internal and external) bacteria in wild copepods (
Acar-
tia
spp. and
Temora
spp.) collected from the German Bight (the south-eastern bight of the
North Sea) and also in laboratory cultured
Acartia tonsa
. DGGE analysis showed distinct
banding patterns for each of the three copepods species analysed. Differences in banding pat-
terns between ground and intact copepods were also observed, suggesting distinct internal and
external bacterial communities. Band sequencing revealed the presence of α-Proteobacteria
related to the
Roseobacter
clade in all types of copepods. Similarly, in
Calanus
spp. sam-
pled in the North Sea, DGGE and 16S rRNA gene sequencing revealed a predominance of
bacteria belonging to the
Roseobacter
clade (Møller
etal.
2007). The fact that bacteria from the
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