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using terrestrial LAB strains of
Lactococcus casei
,
Pediococcus acidilactici
or
Lactobacillus
lactis
, individually or jointly. As rotifers use bacteria as feed, and may utilize bacterial metabo-
lites, it has been hypothesized that enhanced rotifer growth by bacteria can be due to inorganic
nutrients such as phosphorus (Hessen and Andersen 1990), or micronutrients such as vitamin
B
12
(Yu
et al.
1989), produced by the bacteria. The supplementation of LAB can also have a
regulating effect on the microbiota of rotifers. It has been reported that feeding rotifers with
Lb. plantarum
is an effective way to decrease the bacterial counts in rotifers, especially of the
dominant members of the
Vibrionaceae
(Gatesoupe 1991).
The inconvenience of using telluric LAB, such as
Lc. casei
,
P. acidilactici
or
Lb. lactis
,as
probiotics in rotifer cultures is that survival in seawater may be limited and their use would
imply periodical additions to rotifer cultures (Planas
et al.
2004). Autochthonous LAB strains
could avoid this problem. Harzevili
et al.
(1997) used a probiotic
Lactococcus lactis
strain
AR21, with
in vitro
antagonism against
V. anguillarum
, isolated from a rotifer mass culture in
a hatchery. Antagonistic activity of
Lc. lactis
AR21, due to the production of the bacteriocin
diplococcin, counteracted the negative effect of
V. anguillarum
in
in vitro
trials with rotifers.
Other isolated non-LAB strains (an
Alteromonas
strain and unidentified Gram negative strains)
enhanced rotifer growth rates under different feeding regimes in comparison with axenic cul-
tures or control cultures inoculated with microbial communities present in seawater (Douillet
2000b). In a similar approach, Rombaut
et al.
(1999) isolated bacterial strains from rotifers
in well-performing cultures and determined the effect of the isolates under monoaxenic con-
ditions. The addition of some of those strains (which were not identified) enhanced rotifer
growth rate and egg ratio, as compared with the axenic control treatment. This finding was
also observed by Hagiwara
et al.
(1994) when bacterial strains previously isolated from cul-
tures of actively reproducing
B. plicatilis
were delivered to axenic cultures of rotifer. Selected
Pseudomonas
,
Moraxella
or
Micrococcus
strains increased rotifer reproduction by 4-10 fold.
Martínez-Díaz
et al.
(2003) also reported an increase in egg production and growth of axenic
rotifers in the presence of
V. proteolyticus
and
Aeromonas media
strains.
Bacteria isolated from rotifers may also have a positive effect in fish larvae due to
antagonism towards pathogens. For example, Makridis
et al.
(2005) isolated bacterial strains
(
Cytophaga
sp.,
Roseobacter
sp.,
Ruegeria
sp.,
Paracoccus
sp.,
Aeromonas
sp. and
She-
wanella
sp.) from well-performing rotifer cultures, which significantly improved the survival
of unfed sea bream (
Sparus aurata
) larvae compared to control treatment in filtered seawater.
16.5.3 Probiotics in
Artemia
Artemia
can use bacteria as food (Yasuda and Taga 1980; Intriago and Jones 1993)
and although a diet consisting solely of bacteria has not been successfully established
(D'Agostino 1980), it has been demonstrated that selected bacteria improve axenic cultures
of
Artemia
fed with other foods (Douillet 1987). The culture of
Artemia
under non-axenic
conditions results in higher biomass production than under axenic conditions, and coloniza-
tion of bacteria can be essential to fulfil nutritional requirements when some foods such as
rice-bran are used (D'Agostino 1980; Douillet 1987).
Artemia
require lipids and proteins in
early development, proteins and carbohydrates in juvenile and adult stages, and fatty acids
and vitamins for reproduction and growth. Bacteria can be a source of proteins, vitamins
(such as B
12
), essential amino acids, fatty acids, polyamines, enzymes and inorganic nutrients
(Gorospe
et al.
1996; Hessen and Andersen 1990). It has also been hypothesized that bacteria
may also remove toxic metabolic substances from
Artemia
cultures (Verschuere
et al.
1999).
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