Growth Phase Of Culture Research Articles

The impact of physiological state and environmental stress on bacterial load estimation methodologies for Mycobacterium tuberculosis

When processed in solid or liquid medium, tuberculosis patient samples yield different proportions of a heterogenous bacterial community over the duration of treatment. We aimed to derive a relationship between methodologies for bacterial load determination and assess the effect of the growth phase of the parent culture and its exposure to stress on the results. Mycobacterium tuberculosis H37Rv was grown with and without antibiotic (isoniazid or rifampicin) and sampled on day 0, 3, 11 and 21 of growth in broth culture. The bacterial load was estimated by colony counts and the BD BACTEC MGIT system. Linear and nonlinear mixed-effects models were used to describe the relationship between time-to-positivity (TTP) and time-to-growth (TTG) versus colony forming units (CFU), and growth units (GU) versus incubation time in MGIT. For samples with the same CFU, antibiotic-treated and stationary phase cells had a shorter TTP than antibiotic-free controls and early-logarithmic phase cells, respectively. Similarly, stationary phase samples reached higher GUs and had shorter TTG than early-log phase ones. This suggests that there is a population of bacterial cells that can be differentially recovered in liquid medium, giving us insight into the physiological states of the original culture, aiding the interpretation of clinical trial outputs.

Production and utilization of pseudocobalamin in marine Synechococcus cultures and communities.

Cobalamin influences marine microbial communities because an exogenous source is required by most eukaryotic phytoplankton, and demand can exceed supply. Pseudocobalamin is a cobalamin analogue produced and used by most cyanobacteria but is not directly available to eukaryotic phytoplankton. Some microbes can remodel pseudocobalamin into cobalamin, but a scarcity of pseudocobalamin measurements impedes our ability to evaluate its importance for marine cobalamin production. Here, we perform simultaneous measurements of pseudocobalamin and methionine synthase (MetH), the key protein that uses it as a co-factor, in Synechococcus cultures and communities. In Synechococcus sp. WH8102, pseudocobalamin quota decreases in low temperature (17°C) and low nitrogen to phosphorus ratio, while MetH did not. Pseudocobalamin and MetH quotas were influenced by culture methods and growth phase. Despite the variability present in cultures, we found a comparably consistent quota of 300 ± 100 pseudocobalamin molecules per cyanobacterial cell in the Northwest Atlantic Ocean, suggesting that cyanobacterial cell counts may be sufficient to estimate pseudocobalamin inventories in this region. This work offers insights into cellular pseudocobalamin metabolism, environmental and physiological conditions that may influence it, and provides environmental measurements to further our understanding of when and how pseudocobalamin can influence marine microbial communities.

Native Biocrust Cyanobacteria Strains Showing Antagonism against Three Soilborne Pathogenic Fungi.

The biocontrol potential of three native soil cyanobacteria from biological soil crusts (Nostoc commune, Scytonema hyalinum, and Tolypothrix distorta) was tested by means of in vitro mycelial growth inhibition assays for eighteen cyanobacteria-based products against three phytopathogenic soilborne fungi (Phytophthora capsici, Pythium aphanidermatum, and Fusarium oxysporum f. sp. radicis-cucumerinum). Three cyanobacteria-based production factors were considered: (i) cyanobacterium strain, (ii) cyanobacterial culture growth phase, and (iii) different post-harvest treatments: raw cultures, cyanobacterial filtrates, and cyanobacterial extracts. Results showed that any of the factors considered are key points for successfully inhibiting fungal growth. N. commune showed the highest growth inhibition rates for the three phytopathogens; stationary phase treatments produced higher inhibition percentages than logarithmic ones; and all the post-harvest treatments of N. commune at the stationary phase inhibited the growth of P. capsici, up to 77.7%. Thus, N. commune products were tested in planta against P. capsici, but none of the products showed efficacy in delaying the onset nor reducing the damage due to P. capsici, demonstrating the complexity of the in planta assay's success and encouraging further research to design an appropriate scaling up methodology.

Dynamic Energy Budget model for E. coli growth in carbon and nitrogen limitation conditions

The simulations and predictions obtained from mathematical models of bioprocesses conducted by microorganisms are not overvalued. Mechanistic models are bringing a better process understanding and the possibility of simulating unmeasurable variables. The Dynamic Energy Budget (DEB) model is an energy balance that can be formulated for any living organism and can be classified as a structured model. In this study, the DEB model was used to describe E. coli growth in a batch reactor in carbon and nitrogen substrate limitation conditions. The DEB model provides a possibility to follow the changes in the microbes’ cells including their elemental composition and content of some important cell ingredients in different growth phases in substrate limitation conditions which makes it more informative compared to Monod’s model. The model can be used as an optimal choice between Monod-like models and flux-based approaches.Key points• The DEB model can be used to catch changes in elemental composition of E. coli• Bacteria batch culture growth phases can be explained by the DEB model• The DEB model is more informative compared to Monod’s based models

Isolation and characterization of novel acetogenic strains of the genera Terrisporobacter and Acetoanaerobium.

Due to their metabolic versatility in substrate utilization, acetogenic bacteria represent industrially significant production platforms for biotechnological applications such as syngas fermentation, microbial electrosynthesis or transformation of one-carbon substrates. However, acetogenic strains from the genera Terrisporobacter and Acetoanaerobium remained poorly investigated for biotechnological applications. We report the isolation and characterization of four acetogenic Terrisporobacter strains and one Acetoanaerobium strain. All Terrisporobacter isolates showed a characteristic growth pattern under a H2 + CO2 atmosphere. An initial heterotrophic growth phase was followed by a stationary growth phase, where continuous acetate production was indicative of H2-dependent acetogenesis. One of the novel Terrisporobacter isolates obtained from compost (strain COMT) additionally produced ethanol besides acetate in the stationary growth phase in H2-supplemented cultures. Genomic and physiological characterizations showed that strain COMT represented a novel Terrisporobacter species and the name Terrisporobacter vanillatitrophus is proposed (=DSM 116160T = CCOS 2104T). Phylogenomic analysis of the novel isolates and reference strains implied the reclassification of the T. petrolearius/T. hibernicus phylogenomic cluster to the species T. petrolearius and of the A. noterae/A. sticklandii phylogenomic cluster to the species A. sticklandii. Furthermore, we provide first insights into active prophages of acetogens from the genera Terrisporobacter and Acetoanaerobium.

Effect of salinity stress and nitrogen depletion on growth, morphology and toxin production of freshwater cyanobacterium Microcoleus anatoxicus Stancheva & Conklin

AbstractCyanobacterium Microcoleus anatoxicus, isolated from a coastal stream in northern California, produces both anatoxin-a (ATX) and dihydroanatoxin-a (dhATX), responsible for dog deaths, but its environmental preferences are unknown. We tested the effect of environmentally relevant stressors, e.g., salinity enrichment and nitrogen (N) depletion, on mat formation and toxicity of M. anatoxicus during the stationary growth phase in culture. Microcoleus anatoxicus showed broad salinity tolerance and the potential to enter estuaries and produce toxins in mesohaline conditions. Maximum growth was observed in oligohaline waters with salinity of 4.6 ppt. Moderate salinity stress (up to 7.8 ppt) did not affect dhATX production significantly. In contrast, higher salinity above 9.3 ppt had a detrimental effect on cell growth and significantly suppressed dhATX production. Formation of a common polysaccharide sheath covering multiple filaments was characteristic with increased salinity and may provide protection against osmotic stress. Microcoleus anatoxicus grown for 40 days in N-depleted medium formed mats with significantly elevated dhATX and increased ATX concentrations. Phycobilisome degradation was a possible acclimation response to N-limitation, as indicated by distinctly keritomized and pale cells in these cultures. In both experiments, most of the anatoxins were extracellular, probably due to toxin leaking during the stationary growth phase.

Influence of microbially fermented 2´-fucosyllactose on neuronal-like cell activity in an in vitro co-culture system.

2´-Fucosyllactose (2´-FL), the most abundant oligosaccharide in human milk, plays an important role in numerous biological functions, including improved learning. It is not clear, however, whether 2´-FL or a cleavage product could influence neuronal cell activity. Thus, we investigated the effects of 2´-FL, its monosaccharide fucose (Fuc), and microbial fermented 2´-FL and Fuc on the parameters of neuronal cell activity in an intestinal-neuronal transwell co-culture system in vitro. Native 13C-labeled 2´-FL and 13C-Fuc or their metabolites, fermented with Bifidobacterium (B.) longum ssp. infantis and B. breve, which were taken from the lag-, log- and stationary (stat-) growth phases of batch cultures, were applied to the apical compartment of the co-culture system with Caco-2 cells representing the intestinal layer and all-trans-retinoic acid-differentiated SH-SY5Y (SH-SY5YATRA) cells mimicking neuronal-like cells. After 3 h of incubation, the culture medium in the basal compartment was monitored for 13C enrichment by using elemental analysis isotope-ratio mass spectrometry (EA-IRMS) and effects on cell viability, plasma, and mitochondrial membrane potential. The neurotransmitter activation (BDNF, GABA, choline, and glutamate) of SH-SY5YATRA cells was also determined. Furthermore, these effects were also measured by the direct application of 13C-2´-FL and 13C-Fuc to SH-SY5YATRA cells. While no effects on neuronal-like cell activities were observed after intact 2´-FL or Fuc was incubated with SH-SY5YATRA cells, supernatants from the stat-growth phase of 2´-FL, fermented by B. longum ssp. infantis alone and together with B. breve, significantly induced BDNF release from SH-SY5YATRA cells. No such effects were found for 2´-FL, Fuc, or their fermentation products from B. breve. The BDNF release occurred from an enhanced vesicular release, which was confirmed by the use of the Ca2+-channel blocker verapamil. Concomitant with this event, 13C enrichment was also observed in the basal compartment when supernatants from the stat-growth phase of fermentation by B. longum ssp. infantis alone or together with B. breve were used. The results obtained in this study suggest that microbial products of 2´-FL rather than the oligosaccharide itself may influence neuronal cell activities.

Perfil hemato-bioquímico do tambaqui (Colossoma macropomum Cuvier, 1816) comparando diferentes fases de crescimento em cultivo aquapônico

Abstract The aim of this study was to evaluate the haemato-biochemical parameters of tambaqui Colossoma macropomum in different growth phases in an integrated culture with açai Euterpe oleracea. For this, 240 juvenile tambaqui with initial average weight and length of 21.8 ± 7.74 g and 11.28 ± 6.88 cm were cultured in an aquaponic system integrated with açai for 180 days. During the period, 108 healthy tambaquis were sampled and categorized into five distinct growth phases. At each growth phase blood aliquots were collected. The first phase being fish with an average weight of 103.1 ± 5.27 g; second phase with 823.4 ± 42.6 g; third phase with 1087.75 ± 16.38 g; fourth phase with 1402.0 ± 76.6 g and fifth phase with 1815.0±65.1 g. Water quality variables remained within acceptable parameters for both cultures. Erythrocyte was significantly lower in the first and second phase. Haemoglobin was significantly lower in fish in the first phase. Haematocrit remained the same from the second phase onwards. MCV was significantly lower in fish with 1815.0 ± 65.1 g. Plasma glucose levels were significantly lower in the first and second phases. Cholesterol, triglycerides, and total proteins were significantly higher in fish of the fifth phase. AST was significantly lower in fish from the third phase when compared to fish from the first and fifth phases. ALT was significantly higher in fish from the first phase when compared to fish from the third, fourth, and fifth phases. The results are important tools for assessing the health and well-being of tambaqui in future research involving aquaponic cultures.

Evaluation of the Differential Postbiotic Potential of Shewanella putrefaciens Pdp11 Cultured in Several Growing Conditions

The increased knowledge of functional foods has led to the development of a new generation of health products, including those containing probiotics and products derived from them. Shewanella putrefaciens Pdp11 (SpPdp11) is a strain described as a probiotic that exerts important beneficial effects on several farmed fish. However, the use of live probiotic cells in aquaculture has limitations such as uncertain survival and shelf life, which can limit their efficacy. In addition, its efficacy can vary across species and hosts. When probiotics are administered orally, their activity can be affected by the environment present in the host and by interactions with the intestinal microbiota. Furthermore, live cells can also produce undesired substances that may negatively impact the host as well as the risk of potential virulence reversion acquired such as antibiotic resistance. Therefore, new alternatives emerged such as postbiotics. Currently, there is no knowledge about the postbiotic potential of SpPdp11 in the aquaculture industry. Postbiotic refers to the use of bacterial metabolites, including extracellular products (ECPs), to improve host physiology. However, the production of postbiotic metabolites can be affected by various factors such as cultivation conditions, which can affect bacterial metabolism. Thus, the objective of this study was to evaluate the postbiotic potential of ECPs from SpPdp11 under different cultivation conditions, including culture media, temperature, growth phase, and salinity. We analyzed their hydrolytic, antibacterial, antiviral, and cytotoxic capacity on several fish cell lines. The results obtained have demonstrated how each ECP condition can exert a different hydrolytic profile, reduce the biofilm formation by bacterial pathogens relevant to fish, lower the titer of nervous necrosis virus (NNV), and exert a cytotoxic effect on different fish cell lines. In conclusion, the ECPs obtained from SpPdp11 have different capacities depending on the cultivation conditions used. These conditions must be considered in order to recover the maximum number of beneficial capacities or to choose the appropriate conditions for specific activities.

A two-phase approach optimizing productivity for a mAb-producing CHO cell culture process using dynamic response surface methodology models

Fed-batch cell culture processes are common in the biomanufacturing industry due to their ease of development and simplicity of execution in the cGMP environment. One challenge of fed-batch operation is that the physiochemical conditions within the bioreactor do not remain constant throughout a batch but change over time as the viable cell density changes. It is well accepted that fed-batch cultures are multi-phasic, divided into “growth, stationary, and death phases”. Yet, using empirical modeling methods such as response surface models (RSMs) for optimization is still common. While RSMs can identify local performance maxima, they are limited by the time-invariant factors (input parameters) they use. These factors do not change throughout the run. Dynamic RSM (DRSM) models predict the time-dependent impact of the process inputs allowing for the identification of optimized process operations that change with time. Starting with the data sets generated via a traditional Design of Experiments (DoE) design, the DRSM model successfully optimized the peak cell count during the growth phase of culture and then identified a second set of process parameters that optimized productivity during the stationary phase. The resulting process achieved a harvest titer improvement of 28% relative to the base process condition.

Identification of Mispairing Omic Signatures in Chinese Hamster Ovary (CHO) Cells Producing a Tri-Specific Antibody.

Monoclonal antibody-based therapy has shown efficacy against cancer, autoimmune, infectious, and inflammatory diseases. Multispecific antibodies (MsAbs), including trispecifics (tsAbs), offer enhanced therapeutic potential by targeting different epitopes. However, when co-expressed from three or more different polypeptide chains, MsAb production can lead to incorrect chain assembly and co-production of mispaired species with impaired biological activity. Moreover, mispairing carries significant challenges for downstream purification, decreasing yields and increasing the cost of bioprocess development. In this study, quantitative transcriptomics and proteomics analyses were employed to investigate which signaling pathways correlated with low and high mispairing clone signatures. Gene and protein expression profiles of Chinese hamster ovary (CHO) clones producing an tsAb were analyzed in the exponential growth and stationary (tsAb production) phase of fed-batch culture. Functional analysis revealed activated endoplasmic reticulum stress in high mispairing clones in both culture phases, while low mispairing clones exhibited expression profiles indicative of activated protein translation, as well as higher endocytosis and target protein degradation, suggesting the clearance of unfolded proteins through ubiquitin-mediated mechanisms. In addition, through transcriptomic profiling, we identified a group of genes that have the potential to be used as a biomarker panel tool for identifying high mispairing levels in the early stages of bioprocess development.

Effects of citrate-stabilized gold and silver nanoparticles on some safety parameters of Porphyridium cruentum biomass.

Introduction: Our research raises the question of how realistic and safe it is to use gold and silver nanoparticles in biotechnologies to grow microalgae, which will later be used to obtain valuable products. To this purpose, it was necessary to assess the influence of 10 and 20nm Au and Ag nanoparticles stabilized in citrate on the growth of microalga Porphyridium cruentum in a closed cultivation system, as well as some safety parameters of biomass quality obtained under experimental conditions. Methods: Two types of experiments were conducted with the addition of nanoparticles on the first day and the fifth day of the cultivation cycle. Changes in productivity, lipid content, malondialdehyde (MDA), as well as antioxidant activity of microalgae biomass have been monitored in dynamics during the life cycle in a closed culture system. Results: The impact of nanoparticles on the growth curve of microalgae culture was marked by delaying the onset of the exponential growth phase. A significant increase in the content of lipids and MDA in biomass was noted. Excessive accumulation of lipid oxidation products within the first 24h of cultivation resulted in altered antioxidant activity of red algae extracts. Discussion: Citrate-stabilized gold and silver nanoparticles proved to be a stress factor for red microalga Porphyridium cruentum, causing significant changes in both biotechnological and biomass safety parameters. Addition of Au and Ag nanoparticles during the exponential growth phase of porphyridium culture led to an enhanced lipid accumulation and reduced MDA values in biomass.

Rates of iron(III) reduction coupled to elemental sulfur or tetrathionate oxidation by acidophilic microorganisms and detection of sulfur intermediates

Bioleaching processes and acid mine drainage (AMD) generation are mainly driven by aerobic microbial iron(II) and inorganic sulfur/compound oxidation. Dissimilatory iron(III) reduction coupled to sulfur/compound oxidation (DIRSO) by acidophilic microorganisms has been described for anaerobic cultures, but iron reduction was observed under aerobic conditions as well. Aim of this study was to explore reaction rates and mechanisms of this process. Cell-specific iron(III) reduction rates for different Acidithiobacillus (At.) strains during batch culture growth or stationary phase with iron(III) (∼40 mM) as electron acceptor and elemental sulfur or tetrathionate as electron donor (1% or 5 mM, respectively) were determined. The rates were highest under anaerobic conditions for the At. ferrooxidans type strain with 6.8 × 106 and 1.1 × 107 reduced iron(III) ions per second per cell for growth on elemental sulfur and tetrathionate, respectively. The iron(III) reduction rates were somehow lower for the anaerobically sulfur grown archaeon Ferroplasma acidiphilum, and lowest for the sulfur grown At. caldus type strain under aerobic conditions (1.7 × 106 and 7.3 × 104 reduced iron(III) ions per second per cell, respectively). The rates for five strains of At. thiooxidans (aerobe) were in between those for At. ferrooxidans (anaerobe) and At. caldus (aerobe). There was no pronounced pH dependence of iron(III) reduction rates in the range of pH 1.0–1.9 for the type strains of all species but rates increased with increasing pH for four other At. thiooxidans strains. Thiosulfate as sulfur intermediate was found for At. ferrooxidans during anaerobic growths on tetrathionate and iron(III) but not during anaerobic growths on elemental sulfur and iron(III), and a small concentration was measured during aerobic growths on tetrathionate without iron(III). For the At. thiooxidans type strain thiosulfate was found with tetrathionate grown cells under aerobic conditions in presence and absence of iron(III), but not with sulfur grown cells. Evidence for hydrogen sulfide production at low pH was found for the At. ferrooxidans as well as the At. thiooxidans type strains during microaerophilic growth on elemental sulfur and for At. ferrooxidans during anaerobic growths on tetrathionate and iron(III). The occurrence of sulfur compound intermediates supports the hypothesis that chemical reduction of iron(III) ions takes place by sulfur compounds released by the microbial cells.

Euglena gracilis: Biochemical properties of a membrane bound ecto-phosphatase activity modulated by fluoroaluminate complexes and different trophic conditions

The ecto-phosphatases belong to a group of enzymes closely associated with the cell surface that has its catalytic site facing the extracellular environment, where different phosphorylated substrates can be hydrolyzed. In the present work, we biochemically characterized the ecto-phosphatase activity of the freshwater microalgae Euglena gracilis, a model microorganism, ubiquitously distributed and resistant to several environmental stressors. The ecto-phosphatase activity is acidic, stimulated by copper and presents the following apparent kinetic parameters: Km = 2.52 ± 0.12 mM p-NPP and Vmax = 3.62 ± 0.06 nmol p-NP × h−1 × 106 cells. We observed that zinc, orthovanadate, molybdate, fluoride, and inorganic phosphate inhibit the ecto-phosphatase activity with different magnitudes. Fluoroaluminate complexes are also inhibitors of this ecto-phosphatase activity. They can be formed in the enzyme reaction conditions and are likely to occur in a natural environment where E. gracilis can be found. The ecto-phosphatase activity is constant through the culture growth phases and is negatively modulated after continuous subculturing in the dark when a shift from phototrophic to the heterotrophic metabolism is likely. The analysis of those biochemical parameters may contribute to understanding the role of E. gracilis ecto-phosphatase activity in natural environments.

High-quality RNA extraction and the regulation of genes encoding cellulosomes are correlated with growth stage in anaerobic fungi.

Anaerobic fungi produce biomass-degrading enzymes and natural products that are important to harness for several biotechnology applications. Although progress has been made in the development of methods for extracting nucleic acids for genomic and transcriptomic sequencing of these fungi, most studies are limited in that they do not sample multiple fungal growth phases in batch culture. In this study, we establish a method to harvest RNA from fungal monocultures and fungal-methanogen co-cultures, and also determine an optimal time frame for high-quality RNA extraction from anaerobic fungi. Based on RNA quality and quantity targets, the optimal time frame in which to harvest anaerobic fungal monocultures and fungal-methanogen co-cultures for RNA extraction was 2-5 days of growth post-inoculation. When grown on cellulose, the fungal strain Anaeromyces robustus cocultivated with the methanogen Methanobacterium bryantii upregulated genes encoding fungal carbohydrate-active enzymes and other cellulosome components relative to fungal monocultures during this time frame, but expression patterns changed at 24-hour intervals throughout the fungal growth phase. These results demonstrate the importance of establishing methods to extract high-quality RNA from anaerobic fungi at multiple time points during batch cultivation.

Whey and post-frying oil as substrates in the process of microbial lipids obtaining: a value-added product with nutritional benefits

AbstractYarrowia lipolytica has found many biotechnological applications. The species has a number of regulatory mechanisms to maintain cellular homeostasis, enabling biomass growth in complex media. The aim of this study was to evaluate the use of Y. lipolytica yeast as a platform for the simultaneous management of several industrial by-products and the production of microbial lipids with application potential in the chemical and food industries. Batch cultures of KKP 379 strain were conducted in media with post-frying rapeseed oil (PFO) and a by-product of curd cheese production—acid whey. To evaluate the potential of Yarrowia as a nutraceutical, quantitative and qualitative analyses of microbial sterols were carried out along with an assessment of the biomass mineral composition. It was indicated that the composition and content of sterols varied depending on the phase of cell growth in batch culture. During culture in medium with 20% (v/v) whey and 50 g/L PFO, the cellular lipid content reached 39% (w/w). The highest amount of sterols per dry biomass (7.38 mg/g) and cellular lipids (21.08 mg/g) was recorded after 38 h of culture. The dominant was ergosterol 12.10 mg/g (57%). In addition, the composition of carbon and nitrogen sources in the medium affected the content of selected elements in biomass, indicating that substrate modification can be a tool for manipulating the composition of yeast cells. The results of the study showed that the selection of waste substrates is an important factor in regulation of the cellular lipid accumulation efficiency, as well as the content of certain sterols.

Predictive Cell Culture Time Evolution Based on Electric Models.

Obtaining cell concentration measurements from a culture assay by using bioimpedance is a very useful method that can be used to translate impedances to cell concentration values. The purpose of this study was to find a method to obtain the cell concentration values of a given cell culture assay in real time by using an oscillator as the measurement circuit. From a basic cell-electrode model, enhanced models of a cell culture immersed in a saline solution (culture medium) were derived. These models were used as part of a fitting routine to estimate the cell concentration in a cell culture in real time by using the oscillation frequency and amplitude delivered by the measurement circuits proposed by previous authors. Using real experimental data (the frequency and amplitude of oscillations) that were obtained by connecting the cell culture to an oscillator as the load, the fitting routine was simulated, and real-time data of the cell concentration were obtained. These results were compared to concentration data that were obtained by using traditional optical methods for counting. In addition, the error that we obtained was divided and analyzed in two parts: the first part of the experiment (when the few cells were adapting to the culture medium) and the second part of the experiment (when the cells exponentially grew until they completely covered the well). Low error values were obtained during the growth phase of the cell culture (the relevant phase); therefore, the results obtained were considered promising and show that the fitting routine is valid and that the cell concentration can be measured in real time by using an oscillator.

Bimodal Cell Size and Fusing Cells Observed in a Clonal Culture of the Ciguatoxin-Producing Benthic Dinoflagellate Gambierdiscus (WC1/1).

Cells in a clonal culture of the WC1/1 strain of Gambierdiscus that produced ciguatoxin and maitotoxin-3 were observed to spontaneously fuse during the light phase of culture growth. Cells in the process of fusion were indistinguishable from other cells under the light microscope, except that at least one (often both) of the fusing cells displayed an extendible, finger-like protrusion (presumed peduncle) arising from near the sulcul region. Fusion started with one of the cells turning 90° to place the planes of the girdles approximately at right angles to each other, and movement of the transverse flagella ceased in both cells, or in the cell seen in girdle (lateral) view. The cell in girdle view appeared to fuse into the theca of the other cell. The cell that had turned 90° often rounded up and become egg shaped (obovoid) during early fusion. Fusion can be quick (<10 min) or can take more than an hour. We saw no evidence of the theca being shed during fusion. Measurement of the dorsoventral and transdiameters revealed a wide range for cell sizes that were distributed as a bimodal population in the clonal culture. This bimodal cell population structure was maintained in clonal cultures reisolated from a small or large cell from the original WC1/1 culture. Cellular production of ciguatoxins by the WC1/1 clone increased during the first two years in culture with a corresponding decrease in production of maitotoxin-3, but this inverse relationship was not maintained over the following ~1.5 years.

The growth, biochemical composition, and antioxidant response of Microcystis and Chlorella are influenced by Ibuprofen.

Non-steroidal anti-inflammatory drugs like ibuprofen (IBU) are extensively used, causing substantial amounts to end up in aquatic ecosystems. Unfortunately, little research has been done on how these medications influence the physiology of phytoplankton. This study aimed to investigate the toxicological and physiological effects of IBU on the cyanobacteria Microcystis aeruginosa LE3 and Microcystis aeruginosa EAWAG 198, and the chlorophyte Chlorella sorokiniana. Exponential growth phase cultures were exposed to IBU at 10 to 10,000 μg/L for 96 h. The medium effect concentrations revealed varied sensitivity to IBU in the order Chlorella sorokiniana > Microcystis aeruginosa LE3 > Microcystis aeruginosa EAWAG 198. The drug caused a significant difference from control in cell density and chlorophyll-a of the three strains, except for chlorophyll-a in M. aeruginosa EAWAG 198 cultures where a significant difference occurred at 100 μg/L. The cell density of M. aeruginosa LE3 cultures exposed to 10 μg/L IBU increased 24 h post-exposure. Increasing concentrations of IBU induced higher total microcystins content of the Microcystis aeruginosa. Intracellular hydrogen peroxide content, peroxidase, and glutathione S-transferase activities, and lipid peroxidation increased as a function of IBU exposure. Total lipid, carbohydrate, and protein content of Chlorella sorokiniana were stimulated following IBU exposure. We conclude that the increasing presence of IBU in aquatic ecosystems could significantly alter the population dynamics of the investigated and other phytoplankton species.

Transient Complexity of E. coli Lipidome Is Explained by Fatty Acyl Synthesis and Cyclopropanation.

In the case of many bacteria, such as Escherichia coli, the composition of lipid molecules, termed the lipidome, temporally adapts to different environmental conditions and thus modifies membrane properties to permit growth and survival. Details of the relationship between the environment and lipidome composition are lacking, particularly for growing cultures under either favourable or under stress conditions. Here, we highlight compositional lipidome changes by describing the dynamics of molecular species throughout culture-growth phases. We show a steady cyclopropanation of fatty acyl chains, which acts as a driver for lipid diversity. There is a bias for the cyclopropanation of shorter fatty acyl chains (FA 16:1) over longer ones (FA 18:1), which likely reflects a thermodynamic phenomenon. Additionally, we observe a nearly two-fold increase in saturated fatty acyl chains in response to the presence of ampicillin and chloramphenicol, with consequences for membrane fluidity and elasticity, and ultimately bacterial stress tolerance. Our study provides the detailed quantitative lipidome composition of three E. coli strains across culture-growth phases and at the level of the fatty acyl chains and provides a general reference for phospholipid composition changes in response to perturbations. Thus, lipidome diversity is largely transient and the consequence of lipid synthesis and cyclopropanation.