Stoichiometry of Fe, Mn and Co in the marine diazotroph Crocosphaera subtropica ATCC51142 in Fe- and P-limited continuous cultures

2020 ◽  
Vol 656 ◽  
pp. 19-33
Author(s):  
A Marki ◽  
R Fischer ◽  
TJ Browning ◽  
E Louropoulou ◽  
R Ptacnik ◽  
...  
Keyword(s):  
Steady State ◽  
Growth Conditions ◽  
Marine Phytoplankton ◽  
Constant Growth Rate ◽  
Batch Cultures ◽  
Marine Systems ◽  
Elemental Stoichiometry ◽  
State Growth ◽  
Constant Growth

We investigated trace element stoichiometries of the nitrogen-fixing marine cyanobacterium Crocosphaera subtropica ATCC51142 under steady-state growth conditions. We utilized exponentially fed batch cultures and varied iron (Fe) concentrations to establish nutrient limitation in C. subtropica growing at a constant growth rate (0.11 d-1). No statistical difference in cell density, chlorophyll a, particulate organic carbon (C), nitrogen (N) and phosphorus (P) were observed between consecutive days after Day 14, and cultures were assumed to be at steady state with respect to growth for the remaining 11 d of the experiment. Cultures were limited by P in the highest Fe treatment (41 nmol l-1) and by Fe in the 2 lower-concentration Fe treatments (1 and 5 nmol l-1). Cell size and in vivo fluorescence changed throughout the experiment in the 1 nmol l-1 Fe treatment, suggesting ongoing acclimation of C. subtropica to our lowest Fe supply. Nevertheless, Fe:C ratios were not significantly different between the Fe treatments, and we calculated an average (±SD) Fe:C ratio of 32 ± 14 µmol mol-1 for growth at 0.11 d-1. Steady-state P-limited cells had lower P quotas, whilst Fe-limited cells had higher manganese (Mn) and cobalt (Co) quotas. We attribute the increase in Mn and Co quotas at low Fe to a competitive effect resulting from changes in the supply ratio of trace elements. Such an effect has implications for variability in elemental stoichiometry in marine phytoplankton, and potential consequences for trace metal uptake and cycling in marine systems.

scholarly journals Activation of Escherichia coli rRNA Transcription by FIS during a Growth Cycle

1998 ◽  
Vol 180 (6) ◽  
pp. 1525-1532 ◽  
Author(s):  
J. Alex Appleman ◽  
Wilma Ross ◽  
Julia Salomon ◽  
Richard L. Gourse
Keyword(s):  
Escherichia Coli ◽  
Site Occupancy ◽  
Growth Conditions ◽  
Growth Cycle ◽  
Rrna Synthesis ◽  
Rrna Transcription ◽  
Low Culture ◽  
State Growth ◽  
In Vivo Footprinting

ABSTRACT rRNA transcription in Escherichia coli is activated by the FIS protein, which binds upstream of rrnp 1promoters and interacts directly with RNA polymerase. Analysis of the contribution of FIS to rrn transcription under changing physiological conditions is complicated by several factors: the wide variation in cellular FIS concentrations with growth conditions, the contributions of several other regulatory systems to rRNA synthesis, and the pleiotropy of fis mutations. In this report, we show by in vivo footprinting and Western blot analysis that occupancy of the rrnBp 1 FIS sites correlates with cellular levels of FIS. We find, using two methods of measurement (pulse induction of a FIS-activated hybrid promoter and primer extension from an unstable transcript made fromrrnBp 1), that the extent of transcription activation by FIS parallels the degree of FIS site occupancy and therefore cellular FIS levels. FIS activates transcription throughout exponential growth at low culture density, butrrnp 1 transcription increases independently of FIS immediately following upshift, before FIS accumulates. These results support the model that FIS is one of a set of overlapping signals that together contribute to transcription fromrrnp 1 promoters during steady-state growth.

THE ROLE OF CONSECUTIVE BATCH CULTURE IN RUMEN MICROBIOLOGY

1984 ◽  
Vol 64 (5) ◽  
pp. 47-48 ◽  
Author(s):  
M. K. THEODOROU ◽  
D. J. GASCOYNE ◽  
D. E. BEEVER
Keyword(s):  
Steady State ◽  
Microbial Communities ◽  
Microbial Ecology ◽  
Key Words ◽  
Batch Culture ◽  
Rumen Fluid ◽  
Quasi Steady State ◽  
Batch Cultures

Anaerobic, forage-containing medium was inoculated with rumen fluid and consecutive batch cultures were established. Microbial communities were maintained and cultures demonstrated quasi-steady-state. The VFA proportions from consecutive batch cultures which were transferred at 3-day intervals were similar to those obtained in vivo. Key words: Microbial ecology, rumen, batch culture

scholarly journals Lactate and Acrylate Metabolism by Megasphaera elsdenii under Batch and Steady-State Conditions

2012 ◽  
Vol 78 (24) ◽  
pp. 8564-8570 ◽  
Author(s):  
Rupal Prabhu ◽  
Elliot Altman ◽  
Mark A. Eiteman
Keyword(s):  
Steady State ◽  
Double Bond ◽  
Growth Conditions ◽  
Transferase Activity ◽  
Content Type ◽  
Steady State Growth ◽  
Coa Transferase ◽  
Megasphaera Elsdenii ◽  
State Growth ◽  
Acrylate Pathway

ABSTRACTThe growth ofMegasphaera elsdeniion lactate with acrylate and acrylate analogues was studied under batch and steady-state conditions. Under batch conditions, lactate was converted to acetate and propionate, and acrylate was converted into propionate. Acrylate analogues 2-methyl propenoate and 3-butenoate containing a terminal double bond were similarly converted into their respective saturated acids (isobutyrate and butyrate), while crotonate and lactate analogues 3-hydroxybutyrate and (R)-2-hydroxybutyrate were not metabolized. Under carbon-limited steady-state conditions, lactate was converted to acetate and butyrate with no propionate formed. As the acrylate concentration in the feed was increased, butyrate and hydrogen formation decreased and propionate was increasingly generated, while the calculated ATP yield was unchanged.M. elsdeniimetabolism differs substantially under batch and steady-state conditions. The results support the conclusion that propionate is not formed during lactate-limited steady-state growth because of the absence of this substrate to drive the formation of lactyl coenzyme A (CoA) via propionyl-CoA transferase. Acrylate and acrylate analogues are reduced under both batch and steady-state growth conditions after first being converted to thioesters via propionyl-CoA transferase. Our findings demonstrate the central role that CoA transferase activity plays in the utilization of acids byM. elsdeniiand allows us to propose a modified acrylate pathway forM. elsdenii.

scholarly journals MUTATION RATES OF BACTERIA IN STEADY STATE POPULATIONS

1955 ◽  
Vol 39 (2) ◽  
pp. 267-278 ◽  
Author(s):  
Maurice S. Fox
Keyword(s):  
Steady State ◽  
Generation Time ◽  
Growth Conditions ◽  
Complex Medium ◽  
Mutation Rates ◽  
Steady State Growth ◽  
Nutritional Conditions ◽  
Generation Times ◽  
State Growth

The breeder and the chemostat have been used to measure mutation rates for two mutations under a variety of steady state growth conditions. These rates have been found to be higher in complex medium than in minimal (F) medium. The effects of changes in nutritional conditions on these high rates have been described. In addition, the mutation rates at short generation times, in complex medium, have been shown to decrease with increasing generation time.

scholarly journals A Penicillium rubens platform strain for secondary metabolite production

2020 ◽  
Author(s):  
Carsten Pohl ◽  
Fabiola Polli ◽  
Tabea Schütze ◽  
Annarita Viggiano ◽  
László Mózsik ◽  
...  
Keyword(s):  
Secondary Metabolite ◽  
Aromatic Amino Acids ◽  
Gene Clusters ◽  
Growth Conditions ◽  
Biosynthetic Gene Clusters ◽  
State Growth ◽  
Combinatorial Assembly ◽  
High Yields ◽  
Core Genes

AbstractWe present a Penicillium rubens strain with an industrial background in which the four highly expressed biosynthetic gene clusters (BGC) required to produce penicillin, roquefortine, chrysogine and fungisporin were removed. This resulted in a minimal secondary metabolite background. Amino acid pools under steady-state growth conditions showed reduced levels of methionine and increased intracellular aromatic amino acids. Expression profiling of remaining BGC core genes and untargeted mass spectrometry did not identify products from uncharacterized BGCs. This platform strain was repurposed for expression of the recently identified polyketide calbistrin gene cluster and achieved high yields of decumbenone A, B and C. The penicillin BGC could be restored through in vivo assembly with eight DNA segments with short overlaps. Our study paves the way for fast combinatorial assembly and expression of biosynthetic pathways in a fungal strain with low endogenous secondary metabolite burden.

The Influence of the Arsine Source on the Purity of InGaAs Grown by Hydride VPE

1988 ◽  
Vol 144 ◽  
Author(s):  
D. Noel Buckley ◽  
M. M. Matthiesen
Keyword(s):  
Electron Microscopy ◽  
Carrier Concentration ◽  
Molecular Sieves ◽  
Growth Conditions ◽  
Constant Growth Rate ◽  
High Background ◽  
Feed Line ◽  
Hall Effect Measurements ◽  
Constant Growth ◽  
Scanning Electron

ABSTRACTThe relatively high background carrier concentration obtained in unintentionally doped epitaxial layers of III-V materials imposes a limitation on applications of the hydride VPE process. It is usually attributed to impurities in the gas sources. Results are presented for InGaAs grown by hydride VPE using a range of growth conditions. Carrier concentrations and growth rates for the various samples were determined using, respectively, Polaron electrochemical profiler measurements and scanning electron microscopy. It is shown that the observed background carrier concentration increased with increasing input mole fraction of arsine under conditions of constant growth rate. This strongly implicates the arsine feed gas as a predominant source of impurity. Attempts to purify the arsine feed gas using sodium alumina-silicate molecular sieves are described. Polaron electrochemical profiler measurements and Hall effect measurements on samples grown both with and without molecular sieves in the arsine feed line are presented. From a comparison of the corresponding values of carrier concentration and mobility it is shown that Type 4A molecular sieves were not effective in removing dopant impurities from the 4% arsine-hydrogen mixture used.

Sign in / Sign up

Export Citation Format

Share Document