Oligotrophy and pelagic marine bacteria:Facts and fiction

Oligotrophy, or the inability of bacterial cells to propagate at elevated nutrient concentrations, is a controversial phenomenon in microbiology. The exact cause of the unculturability of many indigenous marine bacteria on standard laboratory media has still not been resolved. Unfortunately the physiology of such cells is difficult to investigate as long as high cell density cultures cannot be obtained. An extensive evaluation of experiments relating to oligotrophy and the cultivation of marine bacteria is presented in this review. When incorporating the findings of studies performed with molecular biological methods, the picture emerges that indigenous marine bacteria can be cultivated under certain conditions and that the 'oligotrophic way of life' is a transient characteristic. Although strong generalisations should not be made with respect to a biological system as diverse as the world's oceans, it should be anticipated that cells with unique physiological characteristics appear to exist in the oceanic system. When combining conventional physiological approaches with molecular biological techniques it is feasible to unveil the phenotypes that go with the encountered genotypes. In view of the enormous complexity of the oceanic system this will prove an ambitious, yet resourceful undertaking

Concentrate feeding and ruminal fermentation. 1. Influence of the frequency of feeding concentrates on rumen acid composition, feed intake and milk production.

1. Four cows with rumen cannulae were given 12 kg concentrates daily in 2 equal portions at 0800 and 1530, in one portion of 12 kg at 0800 or in 4 portions of 3 kg each at 0800, 1100, 1400 and 1700 h. Every period lasted 2 weeks. In addition to the concentrates hay was provided at 0900 and 1630 h and was adjusted so that the daily remainder was at least 1 kg. In 1978 experiments were made with concentrates low in starch and sugars (LSS) (23%) and in 1979 with concentrates high in starch and sugars (HSS) (50%). In 1978 when total DM intake, milk production and milk fat content of each milking were estimated daily, the trend in pH and concentration of L-lactic acid in rumen fluid were estimated on the last day of the preliminary period (2 X 6 kg) and on the 1st, 7th and 14th days of the experimental periods (1 X 12 kg and 4 X 3 kg). In 1979 the same estimations were made, but D-lactic acid and volatile fatty acids were also estimated. Compared to 2 X 6 kg concentrates the changeover to daily 1 X 12 kg or 4 X 3 kg concentrates did not result in significant differences in DM intake nor in milk or milk fat production. Within types of concentrates there was hardly any difference in lowest rumen pH between frequencies of concentrate feeding. When HSS concentrates were given pH in rumen fluid tended to be lower than with the LSS concentrates. With 2 X 6 kg HSS concentrates, pH in rumen fluid was for a short time lower than 5.5. Lactic acid concentrations in the rumen fluid reached maximum within 1 h after concentrate feeding and L-lactic acid was 6.5, 5.0 and 2.0 mmol/litre, respectively, for 1 X 12, 2 X 6 and 4 X 3 kg LSS concentrates. For HSS concentrates the values were 4.5, 2.5 and 1.0 mmol/litre. When the HSS concentrates were given maximum concentration of D-lactic acid in rumen fluid were 2.5 to 3 times the L-lactic acid concentration. When lactic acid was not increased D- and L-lactic acid concentrations were similar. At 0800 h the molar ratio of volatile fatty acids (C2:C3:C4) as a percentage of total volatile fatty acids (VFA) in rumen fluid was 62:22:15 and changed gradually to 56:24:20 at 1900 h. Differences in VFA between frequencies of concentrate feeding were small. Total concentrations of VFA did not vary between treatments. (Abstract retrieved from CAB Abstracts by CABI’s permission

Concentrate feeding and ruminal fermentation. 2. Influence of concentrate ingredients on pH and on L-lactate concentration in incubations in vitro with rumen fluid.

2. Rumen fluid was sampled before feeding from cows given hay, diluted with an anaerobic salt solution and added (20 ml) to different amounts (mostly 1 g) of maize gluten meal, maize, citrus pulp, tapioca, beet pulp, coconut expeller or soya bean oilmeal for incubation at 39 deg C. After at least 4 h of incubation there were large differences in pH and lactic acid concentration. The acidotic index of the feeds was influenced by increasing concentration of the substrate. Except with maize meal, there was little effect of particle size on pH and lactic acid concentration. There were differences in effect on pH and lactic acid concentration between different batches of the same feeds, especially with maize meal. Incubations with mixtures of concentrate ingredients showed different pH and lactic acid concentrations from values expected from results with the single ingredients. (Abstract retrieved from CAB Abstracts by CABI’s permission

Opting out increases HIV testing in a large sexually transmitted infections outpatient clinic

In January 2007, opt-out HIV testing replaced provider-initiated testing at the sexually transmitted infections (STI) outpatient clinic in Amsterdam, The Netherlands. The effect of the opt-out strategy on the uptake of HIV testing was studied and factors associated with refusal of HIV testing were identified. Data routinely collected at the STI clinic were analysed separately for men who have sex with men (MSM) and heterosexuals. Logistic regression analysis was used to identify factors associated with opting out. In 2007, 12% of MSM and 4% of heterosexuals with (presumed) negative or unknown HIV serostatus declined HIV testing. Refusals gradually decreased to 7% and 2% by the year end. In 2006, before the introduction of opt-out, 38% of MSM and 27% of heterosexuals declined testing. The proportion of HIV-positive results remained stable among MSM, 3.4% in 2007 versus 3.7% in 2006, and among heterosexuals, 0.2% in 2007 versus 0.3% in 2006. In both groups factors associated with opting out were: age >or=30 years, no previous HIV test, the presence of STI-related complaints and no risky anal/vaginal intercourse. Among heterosexuals, men and non-Dutch visitors refused more often; among MSM, those warned of STI exposure by sexual partners and those diagnosed with gonorrhoea or syphilis refused more often. An opt-out strategy increased the uptake of HIV testing. A sharp increase in testing preceeded a more gradual increase, suggesting time must pass to optimise the new strategy. A small group of visitors, especially MSM, still opt out. Counselling will focus on barriers such as fear and low risk perception among high-risk visitors considering opting ou

Impact of coupled EU support for sugar beet growing: more production, lower prices

In the 2013 negotiations on the ‘new CAP’ (Common Agricultural Policy), the option of voluntary coupled support (VCS) for sugar beet growing was introduced, which has been implemented from 2015 onwards by ten and from 2017 by eleven Member States. In 2017, a great change took place in the EU sugar sector through the abolishment of the sugar quota system, leading to an increase of competition between sugar companies and more fluctuating sugar prices than before. In such a dynamic context, questions were raised about potentially destabilising production and market effects of a VCS-regulation and about its legitimacy

Reducing rural households' annual income fluctuations due to rainfall variation through diversification of wildlife use: portfolio theory in a case study of south eastern Zimbabwe

Annual rural incomes in Southern Africa show large rainfall-induced fluctuations. Variable rainfall has serious implications for agro-pastoral activities (crop cultivation and livestock keeping), whereas wildlife and tourism are less affected. The aim of this paper is to investigate the role of wildlife income in reducing rainfall-induced fluctuations in households’ annual incomes. We analyse costs and benefits from agro-pastoral systems in southeastern Zimbabwe by means of a two-tier longitudinal survey and wildlife benefits through analysis of wildlife revenues. We use the portfolio theory framework to investigate whether wildlife conservation has the potential for farmers to reduce risk associated with agricultural production. Results show that even though wildlife income is small, it tends to be less volatile than income from the agro-pastoral system. Furthermore, the addition of wildlife as an asset to the rural farmers’ portfolio of assets showed that wildlife can be used as a hedge asset to offset risk from agricultural production without compromising on return. The potential of diversification using wildlife is, however, limited since agriculture and wildlife assets are positively correlated. We conclude that revenues from wildlife have some potential to reduce annual household income fluctuations, but only to a limited extent. We argue that if wildlife is organised on a more commercial basis, a more substantial role can be played by wildlife income in reducing variations in rural households’ income

Wildlife as insurance against rainfall fluctuations in a semi-arid savanna setting of southeastern Zimbabwe

This paper presents modeling approaches for wildlife conservation in a semi-arid savanna setting where there are frequent occurrences of drought. The model was used to test the extent to which wildlife income offers opportunities to reduce fluctuations in income as a result of variations in annual rainfall. For the application of the model the wildlife and agro-pastoral systems of southeastern Zimbabwe were simulated. Results show that wildlife income has the potential to compensate for some of the losses in expected income from livestock during droughts. However, wildlife income becomes second best to irrigated agriculture in stabilizing income in areas that show highly fluctuating rainfall. Possible reasons for this include high costs of exploiting the wildlife resource, and the small fraction of wildlife revenues received by households and communities. In order to search for sustainable solutions in areas such as the southeastern low veld of Zimbabwe, it is also important to be aware that the current human population and livestock densities are far above current sustainable levels. Our results therefore suggest that current and future efforts to conserve biodiversity are doomed to fail if there are no efforts made to decongest areas surrounding parks of high densities of human and herbivore populations, and to let local households earn more revenues from wildlif

NK cells in self-limited HCV infection exhibit a more extensively differentiated, but not memory-like, repertoire

Natural killer (NK) cells have long been thought of as a purely innate immune cell population, but increasing reports have described developmental and functional qualities of NK cells that are commonly associated with cells of the adaptive immune system. Of these features, the ability of NK cells to acquire functional qualities associated with immunological memory and continuous differentiation resulting in the formation of specific NK cell repertoires has recently been highlighted in viral infection settings. By making use of a unique cohort of monitored, at-risk intravenous drug users in this study, we were able to dissect the phenotypic and functional parameters associated with NK cell differentiation and NK cell memory in patients 3 years after acute HCV infection and either the subsequent self-clearance or progression to chronicity. We observed increased expression of cytolytic mediators and markers CD56bright and NKp46+ of NK cells in patients with chronic, but not self-limited HCV infection. Patients with a self-limited infection expressed higher levels of differentiation-associated markers CD57 and KIRs, and lower levels of NKG2A. A more extensively differentiated NK cell phenotype is associated with self-clearance in HCV patients, while the NK cells of chronic patients exhibited more naïve and effector NK cell phenotypic and functional characteristics. The identification of these distinct NK cell repertoires may shed light on the role NK cells play in determining the outcome of acute HCV infections, and the underlying immunological defects that lead to chronicity

Ideal Spin Filters: Theoretical Study of Electron Transmission Through Ordered and Disordered Interfaces Between Ferromagnetic Metals and Semiconductors

It is predicted that certain atomically ordered interfaces between some ferromagnetic metals (F) and semiconductors (S) should act as ideal spin filters that transmit electrons only from the majority spin bands or only from the minority spin bands of the F to the S at the Fermi energy, even for F with both majority and minority bands at the Fermi level. Criteria for determining which combinations of F, S and interface should be ideal spin filters are formulated. The criteria depend only on the bulk band structures of the S and F and on the translational symmetries of the S, F and interface. Several examples of systems that meet these criteria to a high degree of precision are identified. Disordered interfaces between F and S are also studied and it is found that intermixing between the S and F can result in interfaces with spin anti-filtering properties, the transmitted electrons being much less spin polarized than those in the ferromagnetic metal at the Fermi energy. A patent application based on this work has been commenced by Simon Fraser University.Comment: RevTeX, 12 pages, 5 figure