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.

Comparative Proteome Profiling of Extracellular Vesicles from Three Growth Phases of Haematococcus pluvialis under High Light and Sodium Acetate Stresses.

Extracellular vesicles (EVs) are nano-sized particles involved in intercellular communications that intrinsically possess many attributes as a modern drug delivery platform. Haematococcus pluvialis-derived EVs (HpEVs) can be potentially exploited as a high-value-added bioproduct during astaxanthin production. The encapsulation of HpEV cargo is a crucial key for the determination of their biological functions and therapeutic potentials. However, little is known about the composition of HpEVs, limiting insights into their biological properties and application characteristics. This study examined the protein composition of HpEVs from three growth phases of H. pluvialis grown under high light (350 µmol·m-2·s-1) and sodium acetate (45 mM) stresses. A total of 2038 proteins were identified, the majority of which were associated with biological processes including signal transduction, cell proliferation, cell metabolism, and the cell response to stress. Comparative analysis indicated that H. pluvialis cells sort variant proteins into HpEVs at different physiological states. It was revealed that HpEVs from the early growth stage of H. pluvialis contain more proteins associated with cellular functions involved in primary metabolite, cell division, and cellular energy metabolism, while HpEVs from the late growth stage of H. pluvialis were enriched in proteins involved in cell wall synthesis and secondary metabolism. This is the first study to report and compare the protein composition of HpEVs from different growth stages of H. pluvialis, providing important information on the development and production of functional microalgal-derived EVs.

Proteomics and metabolic burden analysis to understand the impact of recombinant protein production in E. coli.

The impact of recombinant protein production (RPP) on host cells and the metabolic burden associated with it undermine the efficiency of the production system. This study utilized proteomics to investigate the dynamics of parent and recombinant cells induced at different time points for RPP. The results revealed significant changes in both transcriptional and translational machinery that may have impacted the metabolic burden, growth rate of the culture and the RPP. The timing of protein synthesis induction also played a critical role in the fate of the recombinant protein within the host cell, affecting protein and product yield. The study identified significant differences in the expression of proteins involved in fatty acid and lipid biosynthesis pathways between two E. coli host strains (M15 and DH5⍺), with the E. coli M15 strain demonstrating superior expression characteristics for the recombinant protein. Overall, these findings contribute to the knowledge base for rational strain engineering for optimized recombinant protein production.

Production and release of 2-MIB in Pseudanabaena: Effects of growth phases on cell characteristics and 2-MIB yield.

2-methylisoborneol (2-MIB), a secondary metabolite produced by cyanobacteria, often causes a musty odour in water, threatening the safety of drinking water supplies. This study investigated the effects of the growth phases on the production of 2-MIB by Pseudanabaena. The effects of cell characteristics on the production and release of 2-MIB were also explored. The total 2-MIB concentration increased during the exponential phase and decreased during the declining phase, which was consistent with the changes in cell density. However, the total 2-MIB yield (1.12-1.27 fg cell-1) of Pseudanabaena did not significantly differ throughout the growth cycle (p > 0.05). Meanwhile, the extracellular 2-MIB yield increased significantly from 0.31 fg cell-1 in the exponential phase to 0.76 fg cell-1 in the declining phase (p < 0.05), and the corresponding proportion of extracellular 2-MIB improved from 25.13% to 59.16% (p < 0.05). The surge in extracellular 2-MIB during the declining phase could be attributed to the breaking of the Pseudanabaena filament, as indicated by the decrease in Dmean during cell ageing. The findings of this study contribute to a more inclusive comprehension and management of musty odour issues resulting from cyanobacteria in the water supply.

Impact of LuxS on virulence and pathogenicity in Klebsiella pneumoniae exhibiting varied mucoid phenotypes.

How the LuxS/AI-2 quorum sensing (QS) system influences the pathogenicity of K. pneumoniae is complicated by the heterogeneity of the bacterial mucoid phenotypes. This study aims to explore the LuxS-mediated regulation of the pathogenicity of K. pneumoniae with diverse mucoid phenotypes, including hypermucoid, regular-mucoid, and nonmucoid. The wild-type, luxS knockout, and complemented strains of three K. pneumoniae clinical isolates with distinct mucoid phenotypes were constructed. The results revealed the downregulation of virulence genes of regular-mucoid, and nonmucoid but not hypermucoid strains. The deletion of luxS reduced the pathogenicity of the regular-mucoid, and nonmucoid strains in mice; while in hypermucoid strain, luxS knockout reduced virulence in late growth but enhanced virulence in the early growth phase. Furthermore, the absence of luxS led the regular-mucoid and nonmucoid strains to be more sensitive to the host cell defense, and less biofilm-productive than the wild-type at both the low and high-density growth state. Nevertheless, luxS knockout enhanced the resistances to adhesion and phagocytosis by macrophage as well as serum-killing, of hypermucoid K. pneumoniae at its early low-density growth state, while it was opposite to those in its late high-density growth phase. Collectively, our results suggested that LuxS plays a crucial role in the pathogenicity of K. pneumoniae, and it is highly relevant to the mucoid phenotypes and growth phases of the strains. LuxS probably depresses the capsule in the early low-density phase and promotes the capsule, biofilm, and pathogenicity during the late high-density phase, but inhibits lipopolysaccharide throughout the growth phase, in K. pneumoniae.IMPORTANCECharacterizing the regulation of physiological functions by the LuxS/AI-2 quorum sensing (QS) system in Klebsiella pneumoniae strains will improve our understanding of this important pathogen. The genetic heterogeneity of K. pneumoniae isolates complicates our understanding of its pathogenicity, and the association of LuxS with bacterial pathogenicity has remained poorly addressed in K. pneumoniae. Our results demonstrated strain and growth phase-dependent variation in the contributions of LuxS to the virulence and pathogenicity of K. pneumoniae. Our findings provide new insights into the important contribution of the LuxS/AI-2 QS system to the networks that regulate the pathogenicity of K. pneumoniae. Our study will facilitate our understanding of the regulatory mechanisms of LuxS/AI-2 QS on the pathogenicity of K. pneumoniae under the background of their genetic heterogeneity and help develop new strategies for diminished bacterial virulence within the clinical K. pneumoniae population.

Novel insights into toxin changes associated with the growth of Alexandrium pacificum: Revealing active toxin-secretion ability and toxin cell quota variation.

Paralytic shellfish toxins (PSTs) are widely distributed globally and are produced by Alexandrium pacificum in marine system. However, the characteristics of toxins producing and secreting associated with growth phases are still unclear, especially whether A. pacificum has the ability to actively secrete PSTs is controversial. In this study, variation characteristics of intracellular and extracellular PSTs contents associated with A. pacificum growth phases were investigated thoroughly. The results showed that intracellular and extracellular PSTs contents increased sharply during the exponential phase. But during the stationary phase, the intracellular PSTs content increased by only 26 %, and the extracellular PSTs content did not increase significantly. Since the increase in extracellular PSTs content mainly occurred at the exponential phase, when most cells were living, we speculated that active PSTs secretion of living cells might be an important production pathway of extracellular toxins besides leakage from dead cells. Furthermore, toxin cell quota variation associated with the growth phase was analysed. In the exponential phase, the toxin cell quota first increased and then decreased, with a maximum of 19.02 ± 1.80 fmol/cell at 6 d. However, after entering the stationary phase, this value slowly increased again, suggesting that vigilance should be raised for the plateau of Alexandrium blooms. In addition, cells in the exponential phase mainly produced O-sulfated components such as GTX1&4, cells in the stationary phase mainly produced O-sulfate-free components such as GTX5. In this study, the toxigenic rules of A. pacificum were comprehensively uncovered, which provided theoretical guidance for the prevention and mitigation of A. pacificum blooms.

Diversities and Shifts of Microbial Communities Associated with Farmed Oysters (Crassostrea gigas) and Their Surrounding Environments in Laoshan Bay Marine Ranching, China.

Pacific oysters (Crassostrea gigas) are widely cultured in Chinese marine ranching with high economic value. However, mass death of farmed oysters has occurred frequently in recent years because of diseases and environmental disturbance (e.g., high temperatures). In order to analyze the potential relationships between microorganisms and the death of farmed oysters, we compared the dynamics of bacterial and protist communities in oysters at different growth phases using high-throughput sequencing. The results showed that the microbial communities in farmed oysters significantly changed and were markedly different from microbes in natural oysters and the surrounding environments. The number of biomarker taxa among farmed oysters and their surrounding environments decreased gradually with the growth of oysters. During the mass death of farmed oysters, the microbial communities' abundance of ecological function genes changed, and the correlations among microorganisms disappeared. These results enrich our understanding of the dynamics of microbial communities in farmed oysters at different growth phases, illustrating the characteristics of interactions among microorganisms during the mass death of farmed oysters. Our study is beneficial to promote the healthy aquaculture of oysters.

Valorisation of Roman chamomile (Chamaemelum nobile L.) herb by comprehensive evaluation of hydrodistilled aroma and residual non-volatile fractions.

Valorization of botanicals for the development of natural food-grade ingredients is an important task in terms of sustainability and processing waste reduction. In this study, Roman chamomile (Chamaemelum nobile L.) herb was collected at six different vegetation phases in the period 26 May - 23 August 2019 and subjected to biorefining into the several valuable fractions. The yield of hydro-distilled essential oil (EO) was in the range of 0.22% (intensive vegetative growth) to 0.80% (full flowering). Angelic, isobutyric, butyric and methacrylic acid esters and some monoterpene and sesquiterpene derivatives were the major EO constituents: 3-methylpentyl angelate (20.11-27.56%), methallyl angelate (7.28-10.33%), isoamyl angelate (5.57-9.02%), isobutyl angelate (4.84-6.79%), 2-methylbutyl angelate (3.11-6.32%), 3-methylamyl methacrylate (5.04-6.17%), 3-methylpentyl isobutyrate (4.29-6.64%), 3-methylamyl isobutyrate (4.29-6.64%), α-pinene (1.61-6.37%) and pinocarvone (1.46-4.67%). In order to valorize water soluble and solid EO distillation residues their antioxidant potential was evaluated by several in vitro assays: water extracts were considerably stronger antioxidants than acetone extracts isolated from the solid residues. Water extracts of the plants collected at flowering phases were the strongest antioxidants; their TPC, FRAP and ORAC values were up to 143.2 mg gallic acid equivalents/g, 650, and 5601 µmol TE/g dry extract, respectively, while effective concentrations (EC50) of DPPH• and ABTS•+ scavenging, were down to 0.59 and 0.49 mg/mL, respectively. Among 7 tentatively identified by UPLC/Q-TOF/MS phenolic constituents the intensity of molecular ion of 3,5-dicaffeoyl quinic acid was the largest. The results obtained may assist for developing flavorings, antioxidants and health beneficial preparations from C. nobile extracts.

Analysis of Growth Phases of Enterotoxigenic Escherichia coli Reveals a Distinct Transition Phase before Entry into Early Stationary Phase with Shifts in Tryptophan, Fucose, and Putrescine Metabolism and Degradation of Neurotransmitter Precursors.

Enterotoxigenic Escherichia coli (ETEC) is a major cause of diarrhea in children and adults in endemic areas. Gene regulation of ETEC during growth in vitro and in vivo needs to be further evaluated, and here we describe the full transcriptome and metabolome of ETEC during growth from mid-logarithmic growth to early stationary phase in rich medium (LB medium). We identified specific genes and pathways subjected to rapid transient alterations in gene expression and metabolite production during the transition from logarithmic to stationary growth. The transient phase was found to be different from the subsequent induction of early stationary phase-induced genes. The transient phase was characterized by the repression of genes and metabolites involved in organic substance transport. Genes involved in fucose and putrescine metabolism were upregulated, and genes involved in iron transport were repressed. Expression of toxins and colonization factors were not changed, suggesting retained virulence from mid-logarithmic to the start of the stationary phase. Metabolomic analyses showed that the transient phase was characterized by a drop of intracellular amino acids, e.g., l-tyrosine, l-tryptophan, l-phenylalanine, l-leucine, and l-glutamic acid, followed by increased levels at induction of stationary phase. A pathway enrichment analysis of the entire combined transcriptome and metabolome revealed that significant pathways during progression from logarithmic to early stationary phase are involved in the degradation of neurotransmitters aminobutyrate (GABA) and precursors of 5-hydroxytryptamine (serotonin). This work provides a comprehensive framework for further studies on transcriptional and metabolic regulation in pathogenic E. coli. IMPORTANCE We show that E. coli, exemplified by the pathogenic subspecies enterotoxigenic E. coli (ETEC), undergoes a stepwise transcriptional and metabolic transition into the stationary phase. At a specific entry point, E. coli induces activation and repression of specific pathways. This leads to a rapid decrease of intracellular levels of certain amino acids. The resulting metabolic activity leads to an intense but short peak of indole production, suggesting that this is the previously described "indole peak," rapid decrease of intermediate molecules of bacterial neurotransmitters, increased putrescine and fucose uptake, increased glutathione levels, and decreased iron uptake. This specific transient shift in gene expression and metabolome is short-lived and disappears when bacteria enter the early stationary phase. We suggest that these changes mainly prepare bacteria for ceased growth, but based on the pathways involved, we could suggest that this transient phase substantially influences survival and virulence.

Nst1, Densely Associated to P-Body in the Post-Exponential Phases of Saccharomyces cerevisiae, Shows an Intrinsic Potential of Producing Liquid-Like Condensates of P-Body Components in Cells.

Membrane-less biomolecular compartmentalization is a core phenomenon involved in many physiological activities that occur ubiquitously in cells. Condensates, such as promyelocytic leukemia (PML) bodies, stress granules, and P-bodies (PBs), have been investigated to understand the process of membrane-less cellular compartmentalization. In budding yeast, PBs dispersed in the cytoplasm of exponentially growing cells rapidly accumulate in response to various stresses such as osmotic stress, glucose deficiency, and heat stress. In addition, cells start to accumulate PBs chronically in post-exponential phases. Specific protein-protein interactions are involved in accelerating PB accumulation in each circumstance, and discovering the regulatory mechanism for each is the key to understanding cellular condensation. Here, we demonstrate that Nst1 of budding yeast Saccharomyces cerevisiae is far more densely associated with PBs in post-exponentially growing phases from the diauxic shift to the stationary phase than during glucose deprivation of exponentially growing cells, while the PB marker Dcp2 exhibits a similar degree of condensation under these conditions. Similar to Edc3, ectopic Nst1 overexpression induces self-condensation and the condensation of other PB components, such as Dcp2 and Dhh1, which exhibit liquid-like properties. Altogether, these results suggest that Nst1 has the intrinsic potential for self-condensation and the condensation of other PB components, specifically in post-exponential phases.

Effects of Growing Rod Technique with Different Surgical Modes and Growth Phases on the Treatment Outcome of Early Onset Scoliosis: A 3-D Finite Element Analysis.

Early onset scoliosis (EOS) is emerging as a serious threat to children's health and is the third largest threat to their health after myopia and obesity. At present, the growing rod technique (GRT), which allows patients to regain a well-balanced sagittal profile, is commonly considered as an invasive surgical procedure for the treatment of EOS. However, the risk of postoperative complications and instrumentation breakage remains high, which is mainly related to the choice of fixed mode. Several authors have studied primary stability and instrumentation loads, neglecting the mechanical transmission of the spinal long-segment model in different growth phases, which is fundamental to building a complete biomechanical environment. The present study aimed to investigate the kinematic and biomechanical properties that occur after GRT, across the long spinal structure and the posterior instrumentation, which are affected by unilateral or bilateral fixation. Accordingly, spinal segments (C6-S1) were loaded under flexion (Flex), extension (Ext), left lateral bending (LB), right lateral bending (RB), left torsion (LT), and right torsion (RT) using 11 established spinal models, which were from three growth phases. The stress distribution, spinal and intervertebral range of motion (ROM), counter torque of the vertebra, and bracing force on the rods were measured. The results showed that bilateral posterior fixation (BPF) is more stable than unilateral posterior fixation (UPF), at the expense of more compensations for the superior adjacent segment (SAS), especially when the superior fixed segment is closer to the head. Additionally, the bracing force of the instrumentation on the spine increases as the Cobb angle decreases. Accordingly, this biomechanical analysis provides theoretical suggestions for the selection of BPF or UPF and fixed segments in different growing phases.

Fermentation Efficiency of Genetically Modified Yeasts in Grapes Must.

Winemaking is a stressful procedure for yeast cells. The presence of high levels of carbohydrates at the beginning of the fermentation and the subsequent increase of ethanol levels alongside with other environmental factors force the cell to undergo a continuous adaptation process. Ideally, yeast strains should be able to adapt to this changing environment fast and they must be able to ferment at low temperatures with the highest possible fermentation rates. Additionally, the balanced utilization of glucose and fructose-the two major hexoses in grapes-is also important as any residual fructose may confers unwanted sweetness. As proteins, Msn2/4 are known to play pivotal roles in cell stress response, the question that arise regards the differentially cell response driven by specific point mutations in these two proteins, and the subsequent effects on alcoholic fermentation. Four different mutants in which serine residues have been replaced by alanine are studied in this paper. Our results indicate that substitution at position 533 of Msn4 protein (W_M4_533) significantly increases the fermentation rate even at low temperatures (12 °C), by lowering the fermentation's activation energy. Similar results but to a lesser extent were obtained by the S582A substitution in Msn2 protein. In addition, W_M4_533 seems to have a more balanced utilization of must hexoses. From the present work it is concluded that genetic modification Msn2/4 represents a promising procedure for shortening the fermentation time, even at low temperatures, which in many cases constitutes an important technological requirement.

A comprehensive assessment of fungi in urban sewer biofilms: Community structure, environmental factors, and symbiosis patterns.

Sewers are important parts of wastewater treatment facilities and the fungal microbial communities therein make large contributions to the biotransformation of wastewater. Therefore, this experiment constructed an experimental sewer system and characterized the fungal microbial communities using ITS high-throughput sequencing technology in combination with network structure analysis and statistical correlation analysis methods. The results demonstrated that the overall diversity of the fungal communities gradually increased as growth phases progressed, but the dominant groups differed significantly among phases. In the early growth phase (RS1) the dominant genera were Apiotrichum and Inocybe, with abundances of 34% and 14%, respectively, while the middle and late growth phases (RS2 and RS3) were dominated by Candida, with a relative abundance of 47%-66%. CCA and correlation analysis showed that the fungal communities diversity from the artificial sewers had significant positive correlations with COD (r2 = 0.44, p < 0.05) and NH4+ (r2 = 0.64, p < 0.05) and that environmental factors significantly influenced the abundances of Fusarium and Aspergillus. Network analysis revealed differences in the fungal groups representing key nodes during different periods. Candida, Trichosporon, Fusarium, and Aspergillus played important roles in the microbial ecosystem of the simulated sewer systems. This study provides data-supported insight into the bacterial-fungal interaction mechanisms and associated pollutant biodegradation technologies in sewers.

Monitoring of three-phase variations in the mortality of COVID-19 pandemic using control charts: where does Pakistan stand?

BACKGROUND: At the end of December 2019, the world in general and Wuhan, the industrial hub of China, in particular, experienced the COVID-19 pandemic. Massive increment of cases and deaths occurred in China and 209 countries in Europe, America, Australia, Asia and Pakistan. Pakistan was first hit by COVID-19 when a case was reported in Karachi on 26 February 2020. Several methods were presented to model the death rate due to the COVID-19 pandemic and to forecast the pinnacle of reported deaths. Still, these methods were not used in identifying the first day when Pakistan enters or exits the early exponential growth phase. OBJECTIVE: The present study intends to monitor variations in deaths and identify the growth phases such as pre-growth, growth, and post-growth phases in Pakistan due to the COVID-19 pandemic. METHODS: New approaches are needed that display the death patterns and signal an alarming situation so that corrective actions can be taken before the condition worsens. To meet this purpose, secondary data on daily reported deaths due to the COVID-19 pandemic have been considered, and the $c$ and exponentially weighted moving average (EWMA) control charts are used To meet this purpose, secondary data on daily reported deaths in Pakistan due to the COVID-19 pandemic have been considered. The $ c$ and exponentially weighted moving average (EWMA) control charts have been used for monitoring variations. RESULTS: The chart shows that Pakistan switches from the pre-growth to the growth phase on 31 March 2020. The EWMA chart demonstrates that Pakistan remains in the growth phase from 31 March 2020 to 17 August 2020, with some indications signaling a decrease in deaths. It is found that Pakistan moved to a post-growth phase for a brief period from 27 July 2020 to 28 July 2020. Pakistan switches to re-growth phase with an alarm on 31/7/2020, right after the short-term post-growth phase. The number of deaths starts decreasing in August in that Pakistan may approach the post-growth phase shortly. CONCLUSION: This amalgamation of control charts illustrates a systematic implementation of the charts for government leaders and forefront medical teams to facilitate the rapid detection of daily reported deaths due to COVID-19. Besides government and public health officials, it is also the public's responsibility to follow the enforced standard operating procedures as a temporary remedy of this pandemic in ensuring public safety while awaiting a suitable vaccine to be discovered.

Proteomic analyses of the oleaginous and carotenogenic yeast Rhodotorula diobovata across growth phases under nitrogen- and oxygen-limited conditions.

Carotenoids and triacylglycerols from yeasts are important bioproducts that can be utilized for the nutraceutical and biodiesel industries respectively. Rhodotorula diobovata is capable of producing these bioproducts under varied culture conditions. These productions have been linked to the early stationary growth phase and their levels only start to decline at the late stationary phase when carbon becomes limiting. While nitrogen-limitation influences the onset of lipogenesis, continuous synthesis and accumulation of neutral lipids (triacylglycerides) may be dependent on other culture conditions such as aeration. Proteomic analyses were conducted to enhance our understanding of changes in gene product expression under culture conditions with nitrogen-limitation, coupled with insufficient aeration, and revealed a correlation between the upregulation of proteins in the lipolysis pathways and the reduced synthesis of fatty acids at the early stationary phase. Upregulation of glycolytic pathway enzymes suggested that glucose was quickly converted into pyruvate and then acetyl-CoA. However, acetyl-CoA flux favoured carotenoids biosynthesis over fatty acid synthesis, as cells transitioned into the stationary phase. This work provides insights into how culture conditions influence gene product expression levels, pathway utilization, and end-product synthesis patterns.

Differential Protein Expression in Exponential and Stationary Growth Phases of Mycobacterium avium subsp. hominissuis 104.

Mycobacterium avium complex (MAC) is the most common non-tuberculous mycobacterium (NTM) and causes different types of pulmonary diseases. While genomic and transcriptomic analysis of Mycobacterium avium 104 (M. avium 104) has been extensive, little is known about the proteomics of M. avium 104. We utilized proteomics technology to analyze the changes in the whole proteome of M. avium 104 during exponential and stationary growth phases. We found 12 dys-regulated proteins; the up-regulated protein hits in the stationary phase were involved in aminopeptidase, choline dehydrogenase, oxidoreductase, and ATP binding, while the down-regulated proteins in the stationary phase were acetyl-CoA acetyltransferase, universal stress protein, catalase peroxidase, and elongation factor (Tu). The differently expressed proteins between exponential and stationary phases were implicated in metabolism and stress response, pointing to the functional adaptation of the cells to the environment. Proteomic analysis in different growth phases could participate in understanding the course of infection, the mechanisms of virulence, the means of survival, and the possible targets for treatment.

Generation Times of E. coli Prolong with Increasing Tannin Concentration while the Lag Phase Extends Exponentially.

The current study examines the effect of tannins and tannin extracts on the lag phase duration, growth rate, and generation time of Escherichia coli. Effects of castalagin, vescalagin, gallic acid, Colistizer, tannic acid as well as chestnut, mimosa, and quebracho extracts were determined on E. coli's growth phases using the broth microdilution method and obtained by turbidimetric measurements. E. coli responds to the stress caused by the investigated antimicrobial agents with reduced growth rates, longer generation times, and extended lag phases. Prolongation of the lag phase was relatively small at low tannin concentrations, while it became more pronounced at concentrations above half the MIC. Moreover, for the first time, it was observed that lag time extensions follow a strict exponential relationship with increasing tannin concentrations. This feature is very likely a direct consequence of the tannin complexation of certain essential ions from the growth medium, making them unavailable to E. coli for its growth.

Effects of the water-soluble fraction of the mixture fuel oil/diesel on the microalgae Dunaliella tertiolecta through growth.

There is evidence that water-soluble fraction (WSF) from fuel oil/diesel mixture affects marine microbiota. In order to establish a sequence of WSF effects during microalgal growth, this work aimed to monitor Dunaliella tertiolecta exposed to WSF during 15 days. Three different pigments (chlorophyll a, lutein, and ß-carotene) and four metabolites (protein, lipids, fatty acids, and phenols) were studied, and FTIR spectroscopy was used to determine the biomolecular transitions of lipids and their accumulation. The results show that D. tertiolecta triggered a physiological and biochemical response with changes in growth rate, pigments, phenols, lipids, and proteins of the microalga, although fatty acid profile was unaltered. For all the biochemical parameters altered, there were significant differences with the controls. At the end of the assay, exposed D. tertiolecta showed similar values with the control on all the compounds analyzed, except lipids. FTIR absorbance showed an increase in unsaturated acyl chains within the exposed microalgae, giving support for a possible uptake of hydrocarbons from WSF. Variation in pigments and phenol contents is presented as an integrated antioxidant response to the stress imposed by WSF. Overall, this research provides information about the effects of WSF on D. tertiolecta, and the ability of this microalga to recover after long-term exposure to the water-soluble fraction of fuel oil/diesel.

Live-cell fluorescence imaging reveals dynamic production and loss of bacterial flagella.

Bacterial flagella are nanomachines that drive bacteria motility and taxis in response to environmental changes. Whether flagella are permanent cell structures and, if not, the circumstances and timing of their production and loss during the bacterial life cycle remain poorly understood. Here we used the single polar flagellum of Vibrio alginolyticus as our model and implementing in vivo fluorescence imaging revealed that the percentage of flagellated bacteria (PFB) in a population varies substantially across different growth phases. In the early-exponential phase, the PFB increases rapidly through the widespread production of flagella. In the mid-exponential phase, the PFB peaks at around 76% and the partitioning of flagella between the daughter cells are 1:1 and strictly at the old poles. After entering the stationary phase, the PFB starts to decline, mainly because daughter cells stop making new flagella after cell division. Interestingly, we observed that bacteria can actively abandon flagella after prolonged stationary culturing, though cell division has long been suspended. Further experimental investigations confirmed that flagella were ejected in V. alginolyticus, starting from breakage in the rod. Our results highlight the dynamic production and loss of flagella during the bacterial life cycle. IMPORTANCE: Flagella motility is critical for many bacterial species. The bacterial flagellum is made up of about 20 different types of proteins in its final structure and can be self-assembled. The current understanding of the lifetime and durability of bacterial flagella is very limited. In the present study, we monitored Vibrio alginolyticus flagellar assembly and loss by in vivo fluorescence labeling, and found that the percentage of flagellated bacteria varies substantially across different growth phases. The production of flagella was synchronized with cell growth but stopped when cells entered the stationary phase. Surprisingly, we observed that bacteria can actively abandon flagella after prolonged stationary culturing, as well as in the low glucose buffering medium. We then confirmed the ejection of flagella in V. alginolyticus started with breakage of the rod. Our results highlight the dynamic production and loss of flagella during the bacterial life cycle.

Fungal Growth in Batch Culture - What We Could Benefit If We Start Looking Closer.

Since filamentous fungi rapidly adjust their metabolic properties to environmental changes, a rigorous standardization and characterization of cultivation conditions is necessary to obtain meaningful and reproducible results. In batch cultures, which are commonly characterized according to the classical growth curve in textbooks (i.e., lag, exponential, stationary, and declining phase), this is of special difficulty. Although various studies in literature report atypically shaped growth curves of filamentous fungi in batch culture, systematic investigations on this topic are scarce and deviations are barely mentioned in textbooks. Summarizing approximately a decade of observations of growth characteristics from bioreactor batch grown filamentous fungi - in particular two strains (CBS123.823 and CBS123.824) of Penicillium ochrochloron - we demonstrate with a series of highly standardized bioreactor batch culture experiments that the classical growth curve failed to describe growth dynamics of the studied fungi in this work. The nature of the first exhausted nutrient was of remarkable importance for the resulting shape of the growth curve. In all experiments, online respirometry proved to be a powerful tool to distinguish growth phases and revealed more physiological states than expected from the mere biomass curve. In this respect we discuss why "atypical" shaped growth curves often remain unrecognized and that they might be the rule rather than the exception. Acknowledging the importance of the correct presentation of this complex topic in textbooks, we also propose a modified growth curve scheme to sensitize students for potential alternative shaped growth curves.