Identification, cloning and sequencing of the replication region of Lactococcus lactis ssp. lactis biovar. diacetylactis Bu2 citrate plasmid pSL2

The replication region of the 7.8 kilobase (kb) citrate plasmid pSL2 from Lactococcus lactis ssp. lactis biovar. diacetylactis Bu2 was identified. Deletion derivatives of pSL2 were introduced into plasmid-free strain Bu2-60 and tested for their ability to replicate autonomously. The region necessary for replication was identified by comparison of the pSL2 derivatives, cloned and sequenced. No homologies were detected by comparing the putative Rep protein of pSL2 with replicons of other plasmids of Gram-positive bacteria. A part of an IS-element flanking the replication region was found.     

Docosahexaenoic acid: Measurements in food and dietary exposure

The Dietary Reference Intakes (DRIs) were established to be an indicator of adequacy of dietary nutrients as well as providing levels for adequacy in reducing risk of chronic diseases such as neurodegenerative diseases, cardiovascular diseases, cancers, diabetes mellitus, etc. One particular nutrient that is increasingly discussed as a potential candidate for the generation of a DRI is the omega-3 (n-3) fatty acid docosahexaenoic acid (DHA) due to its potential benefits in reducing risk for cardiovascular disease, role in resolution of inflammation, its importance in cognitive function in infants and inhibiting the progression of neurodegenerative diseases in the elderly. Each reference value refers to and is predicated on estimates of daily nutrient intake and the goal of this paper is to review these intakes. The confidence of these values is critical in establishing dose–response relationships. This paper reports intake values for DHA and examines how these data were generated and the relative confidence in these values. The adult US population is estimated to consume 80–100 mg/d of DHA based on a nationally representative sample of >8400 individuals as part of the National Health and Nutrition Examination Survey (NHANES). This value and those presented for women and men at various ages appear reasonable and should be used as the basis for establishing an Adequate Intake (AI) for DHA.     

Proton release from water oxidation by photosystem II: similar stoichiometries are stabilized in thylakoids and PSII core particles by glycerol

During the four-stepped catalytic cycle of water oxidation by photosystem II (PSII) molecular oxygen is released in only one of the four reaction steps whereas the release of four protons is distributed over all steps. In principle, the pattern of proton production could be taken as indicative of the partial reactions with bound water. In thylakoids the extent and rate of proton release varies as function of the redox transition and of the pH without concomitant variations of the redox pattern. The variation has allowed to discriminate between deprotonation events of peripheral amino acids (Bohr effects) as opposed to the chemical deprotonation of a particular redox cofactor, and of water. In contrast, in thylakoids grown under intermittent light, as well as in PSII core particles the pattern of proton release is flat and independent of the pH. This has been attributed to the lack in these materials of the chlorophyll a,b-binding (CAB) proteins. We now found that a thylakoid-like, oscillatory pattern of proton release was restored simply by the addition of glycerol which modifies the protein–protein interaction. Being a further proof for the electrostatic origin of the greater portion of proton release, this effect will serve as an important tool in further studies of water oxidation.     

Stromal NADH supplied by PHOSPHOGLYCERATE DEHYDROGENASE3 is crucial for photosynthetic performance

During photosynthesis, electrons travel from light-excited chlorophyll molecules along the electron transport chain to the final electron acceptor nicotinamide adenine dinucleotide phosphate (NADP) to form NADPH, which fuels the Calvin–Benson–Bassham cycle (CBBC). To allow photosynthetic reactions to occur flawlessly, a constant resupply of the acceptor NADP is mandatory. Several known stromal mechanisms aid in balancing the redox poise, but none of them utilizes the structurally highly similar coenzyme NAD(H). Using Arabidopsis (Arabidopsis thaliana) as a C₃-model, we describe a pathway that employs the stromal enzyme PHOSPHOGLYCERATE DEHYDROGENASE 3 (PGDH3). We showed that PGDH3 exerts high NAD(H)-specificity and is active in photosynthesizing chloroplasts. PGDH3 withdrew its substrate 3-PGA directly from the CBBC. As a result, electrons become diverted from NADPH via the CBBC into the separate NADH redox pool. pgdh3 loss-of-function mutants revealed an overreduced NADP(H) redox pool but a more oxidized plastid NAD(H) pool compared to wild-type plants. As a result, photosystem I acceptor side limitation increased in pgdh3. Furthermore, pgdh3 plants displayed delayed CBBC activation, changes in nonphotochemical quenching, and altered proton motive force partitioning. Our fluctuating light-stress phenotyping data showed progressing photosystem II damage in pgdh3 mutants, emphasizing the significance of PGDH3 for plant performance under natural light environments. In summary, this study reveals an NAD(H)-specific mechanism in the stroma that aids in balancing the chloroplast redox poise. Consequently, the stromal NAD(H) pool may provide a promising target to manipulate plant photosynthesis.

PHOSPHOGLYCERATE DEHYDROGENASE 3, an oxidoreductase in leaf chloroplasts with strong preference to reduce the stromal NAD(H) instead of the NADP(H) pool, is required for full photosynthetic capacity.     

Palynological investigations into the Late Pleistocene and Holocene history of vegetation and settlement at the Löddigsee, Mecklenburg, Germany

A Late Pleistocene and Holocene sediment core from the nowadays terrestrialised portion of the Löddigsee in Southern Mecklenburg, Germany was palynologically investigated. The lake is situated in the rarely investigated Young moraine area at the transition from the Weichselian to the Saalian glaciation. The high-resolution pollen diagram contributes to the establishment of the north-eastern German Late Pleistocene pollen stratigraphy. The vegetation distribution pattern after the end of the Weichselian is in good agreement with other studies from North-eastern Germany, but also has its own characteristics. The Holocene vegetation development reveals features from the north-eastern and north-western German lowlands. A special focus was laid on the environmental history of the two settlements on an island within the lake (Late Neolithic and Younger Slavic period), which were preserved under moist conditions. Both settlements were constructed during a period of low lake level. Although there is evidence of agriculture in the area during the respective periods, the two island settlements seem to have served other purposes.