3,346 research outputs found
In-work support: What is the role of in-work support in a successful transition to sustained employment?
The circumstances of persistently poor families with children: evidence from the Families and Children Study (facs)
Edward Eggletson: Sources and Backgrounds of His Novels
Since Edward Eggleston’s materials for his Hoosier novels are based upon his own experiences and observations, it is necessary to know something of him in his actual environment. To understand how the events and conditions equipped him to be the fictional historian of this part of the Middle West, a rapid survey of his biography is essential
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Integrating the language arts into the history-social science curriculum to develop critical thinking in children
This project has developed a resource guide that will help kindergarten, first, and second grade teachers implement an integrated history-social science curriculum that encourages children to become critical thinkers
Lifelong guidance policy and practice in the EU
A study on lifelong guidance (LLG) policy and practice in the EU focusing on trends, challenges and opportunities. Lifelong guidance aims to provide career development support for individuals of all ages, at all career stages. It includes careers information, advice, counselling, assessment of skills and mentoring
Working Futures 2017-2027: Long-run labour market and skills projections for the UK: February 2020
ECO-PHYSIOLOGY OF THE ENDOSYMBIONT-BEARING LUCINID BIVALVE, CODAKIA ORBICULATA
The lucinid bivalve Codakia orbiculata, whose gills
contain sulphur-oxidizing symbiotic bacteria, occurs in high densities (500/m2) in the rhizosphere of shallow-water
Thalassia testudinum sediments in Bermuda. Both sulphide and
thiosulphate stimulate aerobic respiration in the isolated
bacterial symbionts of C. orbiculata. Sulphide and
thiosulphate stimulate anaerobic ^^COa fixation in bacteria isolated from sulphur-starved bivalves. Interstitial water
sulphide concentrations in the bivalves' habitat reach 300 pM,
and sulphate-reduction rates are high, but thiosulphate
concentrations are low (0.66-32.27 pM) . Thiosulphate supplied
to the symbionts in vivo must be produced by sulphide
oxidation, possibly by the host bivalve. Isolated symbionts
also respire aerobically and fix i * C02 in the absence of
exogenous reduced sulphur, suggesting utilization of
intracellular elemental sulphur stores.
Codakia orbiculata symbiotic bacteria are able to respire
nitrate. Nitrate concentrations in the interstitial water of
C. orbiculata habitat can reach 36 pM. Thiosulphate stimulates
nitrate respiration in the intact symbiosis, incubated in oxic
and anoxic conditions, and in anoxic incubations of isolated
symbionts. Intracellular elemental sulphur is also used by the
•bacteria as a substrate in nitrate respiration. Nitrate
respiration in the absence of exogenous nitrate suggests that
the sjnnbionts may have a limited ability to store nitrate.
There is no direct evidence that sulphide stimulates
nitrate respiration in either the isolated symbionts or the
intact symbiosis, incubated in anoxic conditions. Nitrite
respiration in the symbionts is stimulated by sulphide (only),
however. Because nitrate respiration was measured by nitrite
accumulation, complete denitrification would explain the
apparent failure of sulphide to stimulate nitrate respiration.
High nitrate respiration rates in the intact symbiosis,
incubated with sulphide in oxic conditions, may be in response
to thiosulphate, supplied to the bacterial symbionts after
host oxidation of sulphide. Nitrite respiration in the intact
symbiosis, even when incubated in oxic conditions,
demonstrates that the symbionts have access to some sulphide
in vivo, however, and that host sulphide-oxidation may not be-
100% efficient.
Nitrate and nitrite respiration in the intact symbiosis,
even when incubated in oxic conditions, suggests that the
bacteria may be exposed to low oxygen levels in vivo and may
require the ability to utilize an alternate electron acceptor.
Like some free - living bacteria , Codakia orbiculata bacterial
symbionts may co-respire, or alternately respire , oxygen and
nitrate . The Thalassia testudinum sediments in Bermuda may be
ideal for this bacteria-bivalve symbiosis due to the
availability of oxygen, nitrate and sulphide.Plymouth Marine Laboratory; Bermuda Biological Station for Research, Inc
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