Vitamin B12 and marine ecology
TL;DR: In this paper, the specific growth rate depended on the cell quota according to the relation between the relation of vitamin B12 requirement and medium concentration rather than directly on the medium concentration.
Abstract: 1. Parameters of vitamin B12 requirement ofSkeletonema costatum were measured in continuous culture and compared with those ofMonochrysis lutheri. 2. The specific growth rate depended on the cell quota according to the relation
$$\mu = \mu _m \left( {1 - \frac{{k_Q }}{Q}} \right)$$
rather than directly on the medium concentration.
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TL;DR: Although significant literature exists on microalgal growth and biochemistry, significantly more work needs to be undertaken to understand and potentially manipulate algal lipid metabolism, which means simulations that incorporate financial elements are likely to be increasingly useful for predicting reactor design efficiency and life cycle analysis.
Abstract: Microalgae provide various potential advantages for biofuel production when compared with ‘traditional’ crops. Specifically, large-scale microalgal culture need not compete for arable land, while in theory their productivity is greater. In consequence, there has been resurgence in interest and a proliferation of algae fuel projects. However, while on a theoretical basis, microalgae may produce between 10- and 100-fold more oil per acre, such capacities have not been validated on a commercial scale. We critically review current designs of algal culture facilities, including photobioreactors and open ponds, with regards to photosynthetic productivity and associated biomass and oil production and include an analysis of alternative approaches using models, balancing space needs, productivity and biomass concentrations, together with nutrient requirements. In the light of the current interest in synthetic genomics and genetic modifications, we also evaluate the options for potential metabolic engineering of the lipid biosynthesis pathways of microalgae. We conclude that although significant literature exists on microalgal growth and biochemistry, significantly more work needs to be undertaken to understand and potentially manipulate algal lipid metabolism. Furthermore, with regards to chemical upgrading of algal lipids and biomass, we describe alternative fuel synthesis routes, and discuss and evaluate the application of catalysts traditionally used for plant oils. Simulations that incorporate financial elements, along with fluid dynamics and algae growth models, are likely to be increasingly useful for predicting reactor design efficiency and life cycle analysis to determine the viability of the various options for large-scale culture. The greatest potential for cost reduction and increased yields most probably lies within closed or hybrid closed–open production systems.
849 citations
TL;DR: An empirical relation relating specific growth, rate in steady state systems to nutrient status with respect to more than one nutrient simultaneously is proposed, based on 3 experimentally verifiable postulates.
Abstract: SUMMARY
An empirical relation relating specific growth, rate in steady state systems to nutrient status with respect to more than one nutrient simultaneously is proposed, based on 3 experimentally verifiable postulates: (1) that uptake depends on the external substrate concentration; (2) that growth depends on the interval substrate concentration; and (3) in a steady state system specific rate of uptake (in the absence of significant, excretion) is necessarily the product of the specific growth rate and internal substrate concentration. The implications of this model are discussed in particular in respect to the concept of luxury consumption and Liebig's law of minimum. Some aspects of uptake in transient situations are also discussed.
817 citations
TL;DR: Deciphering the languages of diatoms and bacteria and how they interact will inform the understanding of the role these organisms have in shaping the ocean and how these interactions may change in future oceans.
Abstract: SUMMARY Diatoms and bacteria have cooccurred in common habitats for hundreds of millions of years, thus fostering specific associations and interactions with global biogeochemical consequences. Diatoms are responsible for one-fifth of the photosynthesis on Earth, while bacteria remineralize a large portion of this fixed carbon in the oceans. Through their coexistence, diatoms and bacteria cycle nutrients between oxidized and reduced states, impacting bioavailability and ultimately feeding higher trophic levels. Here we present an overview of how diatoms and bacteria interact and the implications of these interactions. We emphasize that heterotrophic bacteria in the oceans that are consistently associated with diatoms are confined to two phyla. These consistent bacterial associations result from encounter mechanisms that occur within a microscale environment surrounding a diatom cell. We review signaling mechanisms that occur in this microenvironment to pave the way for specific interactions. Finally, we discuss known interactions between diatoms and bacteria and exciting new directions and research opportunities in this field. Throughout the review, we emphasize new technological advances that will help in the discovery of new interactions. Deciphering the languages of diatoms and bacteria and how they interact will inform our understanding of the role these organisms have in shaping the ocean and how these interactions may change in future oceans.
750 citations
TL;DR: In this article, the relation between growth rate, the rate of nutrient uptake and internal and external nutrient concentrations of two nutrients simultaneously was studied in a chemostat population, where the limiting nutrient was the one that showed the smallest cell quota: subsistence quota ratio.
Abstract: Chemostats were used to study the relation between growth rate, the rate of nutrient uptake and internal and external nutrient concentrations of two nutrients simultaneously. (Monochrysis lutheri: phosphorus and vitamin B12.)Growth rate and internal concentrations of both limiting and excess nutrients are related by simple rectangular hyperbolas.Control was shown to follow a threshold rather than multiplicative pattern; that is, non-limiting nutrients exert no control at all over the pattern of growth. The limiting nutrient was the one that showed the smallest cell quota: subsistence quota ratio.Monochrysis populations exhibited two modes of growth. ‘Slow adapted cells’ differed from ‘fast adapted cells’ in the values of the constants for the above relation.Uptake of both limiting and non-limiting nutrients was found to be controlled by internal as well as external substrate concentrations. There was thus a limit to luxury consumption of one nutrient when growth was limited by another.The mathematical model formulated for growth in a chemostat (equations (23)–(29)) allowed prediction of external and internal substrate concentrations and rates of uptake of two nutrients and of biomass, given only the input concentrations of the two nutrients and the dilution rate. This model should apply equally well to growth in batch cultures; its possible application to natural populations was discussed.
721 citations
TL;DR: The main focus is on the three most significant nutrients, i.e. carbon, nitrogen and phosphorus, and their uptake by microalgae and cyanobacteria; however other nutrients are also reviewed.
401 citations
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TL;DR: It is concluded that continuous culture may usually be expected to show a five to tenfold increase in output as compared with a batch process.
Abstract: SUMMARY: A theoretical treatment of continuous culture is given, which allows quantitative prediction of the steady-state concentrations of bacteria and substrate in the culture, and how these may be expected to vary with change of medium, concentration and flow-rate. The layout and operation of a small pilot plant for the continuous culture of bacteria are described. This plant has been operated continuously for periods of up to 4 months without breakdown or contamination of the culture. No alterations in the properties of the organisms studied have occurred during such periods of continuous culture. Results are given of a series of experiments on the continuous culture of Aerobacter cloacae in a chemically defined medium, designed to allow quantitative comparison with the results predicted by the theory. The relative advantages of batch and continuous culture as production processes are discussed, and it is concluded that continuous culture may usually be expected to show a five to tenfold increase in output as compared with a batch process.
974 citations
TL;DR: Specific growth rate in the chemostats was found not to depend directly on medium substrate concentration but on the concentration within the cells (cell quota), obeying a hyperbolic equation of the form
Abstract: 57Co-labelled vitamin B12 was used to study the kinetics of vitamin B12 limitation in Monochrysis lutheri in continuous and exponentially growing batch cultures and in washed cell suspensions.Specific growth rate in the chemostats was found not to depend directly on medium substrate concentration but on the concentration within the cells (cell quota), obeying a hyperbolic equation of the form
814 citations
TL;DR: It is suggested that initial uptake of nitrate is very rapid compared to the next synthesis step and thus that the concentration of some form of internal rather than environmental nitrogen controls growth rate when the nitrogen supply is limiting.
Abstract: Data are presented from two continuous culture experiments with Isochrysis galbana using nitrate as limiting nutrient. It is suggested that initial uptake of nitrate is very rapid compared to the next synthesis step and thus that the concentration of some form of internal rather than environmental nitrogen controls growth rate when the nitrogen supply is limiting. Under this assumption the steady state growth rates are shown to fit a hyperbolic curve relating growth rate to the inferred internal nitrogen concentration. See full-text article at JSTOR
166 citations
TL;DR: Internal inconsistencies in the chemostat's operation indicate the presence of factors not accounted for by theory, and it is argued that only factors analogous to the release of protein-bound vitamin into the medium could in principle account for all the discrepancies.
Abstract: A 250 ml. chemostat has been used to measure the parameters of vitamin B requirement in the chrysomonad Monochrysis lutheri.The yield constant was ca. 0·25 × 10 cells/μμg., i.e. one-third of the figure previously measured in batch cultures.The saturation constant lay between 2 and 6 μμ/ml., i.e. at least twenty times the figure indicated by previous batch culture measurements.Internal inconsistencies in the chemostat's operation indicate the presence of factors not accounted for by theory.It is argued that only factors analogous to the release of protein-bound vitamin into the medium could in principle account for all the discrepancies.
56 citations