Biphasic Growth Research Articles

Mixed Epithelial and Stromal Tumors of the Kidney: An Overview

Mixed epithelial and stromal tumor of the kidney is a recently recognized distinct neoplasm that should be distinguished from other renal neoplasms. These tumors are relatively rare with a female preponderance. Imaging studies are not diagnostic but reveal a solid or solid and cystic mass in most cases. Histopathologically, these tumors reveal biphasic growth pattern comprising mesenchymal and epithelial elements with characteristic estrogen and progesterone receptor immunoreactive mesenchyme reminiscent of ovarian stroma. Malignant transformation, recurrence, and metastasis are rare; however, recently a few cases of malignant mixed epithelial and stromal tumors have been reported in the literature. Recently a case with translocation t(1;19) has been described. This article provides a brief overview of the current knowledge of mixed epithelial and stromal tumor of the kidney.

Mixed epithelial and stromal tumors of the kidney: an overview.

Mixed epithelial and stromal tumor of the kidney is a recently recognized distinct neoplasm that should be distinguished from other renal neoplasms. These tumors are relatively rare with a female preponderance. Imaging studies are not diagnostic but reveal a solid or solid and cystic mass in most cases. Histopathologically, these tumors reveal biphasic growth pattern comprising mesenchymal and epithelial elements with characteristic estrogen and progesterone receptor immunoreactive mesenchyme reminiscent of ovarian stroma. Malignant transformation, recurrence, and metastasis are rare; however, recently a few cases of malignant mixed epithelial and stromal tumors have been reported in the literature. Recently a case with translocation t(1;19) has been described. This article provides a brief overview of the current knowledge of mixed epithelial and stromal tumor of the kidney.

Hormetic effect(s) of tetracyclines as environmental contaminant on Zea mays

Animal wastes from intensive pig farming as fertilizers may expose crops to antimicrobials. Zea mays cultivations were carried out on a virgin field, subjected to dressing with pig slurries contaminated at 15 mg L −1 of Oxy- and 5 mg L −1 of Chlor-tetracycline, and at 8 mg L −1 of Oxy and 3 mg L −1 of Chlor, respectively. Pot cultivation was performed outdoor (Oxy in the range 62.5–1000 ng g −1 dry soil) and plants harvested after 45 days. Tetracyclines analyses on soils and on field plants (roots, stalks, and leaves) did not determine the appreciable presence of tetracyclines. Residues were found in the 45-day pot corn only, in the range of 1–50 ng g −1 for Oxy in roots, accounting for a 5% carry-over rate, on average. Although no detectable residues in plants from on land cultivations, both experimental batches showed the same biphasic growth form corresponding to a dose/response hormetic curve.

Eco-genetic model to explore fishing-induced ecological and evolutionary effects on growth and maturation schedules.

Eco-genetic individual-based models involve tracking the ecological dynamics of simulated individual organisms that are in part characterized by heritable parameters. We developed an eco-genetic individual-based model to explore ecological and evolutionary interactions of fish growth and maturation schedules. Our model is flexible and allows for exploration of the effects of heritable growth rates (based on von Bertalanffy and biphasic growth patterns), heritable maturation schedules (based on maturation reaction norm concepts), or both on individual- and population-level traits. In baseline simulations with rather simple ecological trade-offs and over a relatively short time period (<200 simulation years), simulated male and female fish evolve differential genetic growth and maturation. Further, resulting patterns of genetically determined growth and maturation are influenced by mortality rate and density-dependent processes, and maturation and growth parameters interact to mediate the evolution of one another. Subsequent to baseline simulations, we conducted experimental simulations to mimic fisheries harvest with two size-limits (targeting large or small fish), an array of fishing mortality rates, and assuming a deterministic or stochastic environment. Our results suggest that fishing with either size-limit may induce considerable changes in life-history trait expression (maturation schedules and growth rates), recruitment, and population abundance and structure. However, targeting large fish would cause more adverse genetic effects and may lead to a population less resilient to environmental stochasticity.

The Dual-Functioning Fumarate Reductase Is the Sole Succinate:Quinone Reductase in Campylobacter jejuni and Is Required for Full Host Colonization

Campylobacter jejuni encodes all the enzymes necessary for a complete oxidative tricarboxylic acid (TCA) cycle. Because of its inability to utilize glucose, C. jejuni relies exclusively on amino acids as the source of reduced carbon, and they are incorporated into central carbon metabolism. The oxidation of succinate to fumarate is a key step in the oxidative TCA cycle. C. jejuni encodes enzymes annotated as a fumarate reductase (Cj0408 to Cj0410) and a succinate dehydrogenase (Cj0437 to Cj0439). Null alleles in the genes encoding each enzyme were constructed. Both enzymes contributed to the total fumarate reductase activity in vitro. The frdA::cat(+) strain was completely deficient in succinate dehydrogenase activity in vitro and was unable to perform whole-cell succinate-dependent respiration. The sdhA::cat(+) strain exhibited wild-type levels of succinate dehydrogenase activity both in vivo and in vitro. These data indicate that Frd is the only succinate dehydrogenase in C. jejuni and that the protein annotated as a succinate dehydrogenase has been misannotated. The frdA::cat(+) strain was also unable to grow with the characteristic wild-type biphasic growth pattern and exhibited only the first growth phase, which is marked by the consumption of aspartate, serine, and associated organic acids. Substrates consumed in the second growth phase (glutamate, proline, and associated organic acids) were not catabolized by the the frdA::cat(+) strain, indicating that the oxidation of succinate is a crucial step in metabolism of these substrates. Chicken colonization trials confirmed the in vivo importance of succinate oxidation, as the frdA::cat(+) strain colonized chickens at significantly lower levels than the wild type, while the sdhA::cat(+) strain colonized chickens at wild-type levels.

Chitobiose utilization in Borrelia burgdorferi is dually regulated by RpoD and RpoS

BackgroundBorrelia burgdorferi has limited biosynthetic capabilities and must scavenge N-acetylglucosamine (GlcNAc), an essential component of the microbial cell wall, from the surrounding environment. Spirochetes cultured in the absence of free GlcNAc exhibit biphasic growth; however, addition of chitobiose (a dimer of GlcNAc) substitutes for free GlcNAc resulting in a single exponential phase. We evaluated the effect of RpoS and RpoN, the only alternative sigma factors in B. burgdorferi, on biphasic growth and chitobiose utilization in the absence of free GlcNAc. In addition, we investigated the source of GlcNAc in the second exponential phase.ResultsBy comparing the growth of wild-type cells to insertional mutants for rpoS and rpoN we determined that RpoS, but not RpoN, partially regulates both biphasic growth and chitobiose utilization. The rpoS mutant, cultured in the absence of free GlcNAc, exhibited a significant delay in the ability to initiate a second exponential phase compared to the wild type and rpoS complemented mutant. Expression analysis of chbC, which encodes the membrane-spanning protein of the chitobiose phosphotransferase system, suggests the delay is due to the inability of the rpoS mutant to up regulate chbC. Furthermore, supplementing GlcNAc starved cultures with high concentrations (75 or 150 μM) of chitobiose resulted in biphasic growth of the rpoS mutant compared to a single exponential phase for the wild type and rpoS complemented mutant. In contrast, growth of the rpoN mutant under all conditions was similar to the wild type. 5' Rapid amplification of cDNA ends (5' RACE) revealed the transcriptional start site for chbC to be 42 bp upstream of the translational start site. Analysis of the chbC promoter region revealed homology to previously described RpoD and RpoS B. burgdorferi promoters. We also determined that yeastolate, a component of the growth medium (BSK-II), is not essential for second exponential phase growth.ConclusionTogether these results suggest that RpoD and RpoS, but not RpoN, regulate biphasic growth and chitobiose utilization in B. burgdorferi by regulating the expression of the chitobiose transporter (chbC). The data also demonstrate that the second exponential phase observed in wild-type cells in the absence of free GlcNAc is not due to free chitobiose or GlcNAc oligomers present in the medium.

Analyzing the functional association among seed traits, berry growth and chemical composition in Cabernet-Sauvignon berry (&lt;em&gt;Vitis vinifera&lt;/em&gt; L.) using a mathematical growth function

&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Aims&lt;/strong&gt;: This study aimed at assessing the functional linkage among seed traits (including seed number, seed weight), berry growth and berry sugar and acid concentration by adapting a mathematical growth function with parameters having biological importance.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Methods and results&lt;/strong&gt;: The evolution of berry diameter of Cabernet- Sauvignon was satisfactorily fitted to a bi-phasic growth function with six parameters. Correlations between the parameters and berry characteristics, including time of skin color change, seed number, seed weight, final berry size and chemical composition, were analyzed. Results showed that berry growth within a bunch deviated according to seed number, which positively related to parameters describing diameter increment (D1) and initial growth rate (GRini) during the first rapid growth phase, but not related to any parameters involved in the second growth phase. The time of skin color change was negatively associated with mean seed weight, and coincided with growth parameter DABmax that denotes the time when growth rate is maximum during the second rapid growth phase. Sugar concentration was negatively correlated to final berry fresh weight (BFW), seed fresh weight (SFW), GRini and diameter increment during the second rapid growth phase (D2). Path analysis further revealed that the negative effects of SFW and D2 were indirectly mediated via BFW and GRini.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Conclusions&lt;/strong&gt;: We thus conclude that seed affects berry growth and exerts its influence only during the first growth phase via modifying the parameters D1 and GRini. The time of colour change is also affected by seed, and might not be a good indicator of growth restoration after the lag phase. Sugar concentration is linked to final berry size, specific berry growth parameters and seed weight, for the last mainly in an indirect manner.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Significance of the study&lt;/strong&gt;: This study, integrating the analysis of berry growth and composition with a mathematical growth function, provides a valuable approach for deeper understanding of the functional associations among seed traits, berry growth and berry sugar and acid concentration at the berry level.&lt;/p&gt;

Physiological comparison of Pseudomonas putida between two growth phases during cometabolism of 4‐chlorophenol in presence of phenol and glutamate: a proteomics approach

AbstractBACKGROUND: In cometabolic transformation of 4‐chlorophenol (4‐cp) in the presence of phenol and sodium glutamate (SG), a new biphasic growth pattern has been reported. This study investigates the physiological changes of Pseudomonas putida P8 during the biphasic growth by means of 2‐dimensional gel electrophoresis (2‐DE) and MALDI‐TOF analyses.RESULTS: A total of 49 protein spots were selected and identified in the 2‐DE gels from P. putida P8 grown on a mixed substrate containing 200 mg L−1 of phenol, 200 mg L−1 of 4‐cp and 1000 mg L−1 SG. Among them, 16 protein spots were found differentially expressed in the two exponential growth phases during the biphasic growth, including six catabolic enzymes (DmpC, DmpD, DmpE, DmpF, DmpG and AspA) for substrate utilization. The expression of other proteins involved in detoxification and stress responses, carbohydrate and energy metabolism, and environmental information processing as well as a multifunctional xenobiotic reductase (XenA) was quantitatively analyzed and discussed.CONCLUSION: The expression levels of the identified catabolic enzymes during growth in the two growth phases correlated well with the substrate utilization patterns observed in previous kinetics studies. Furthermore, the results show that cells growing on a mixture of aromatic substrates undergo significant physiological changes. Copyright © 2009 Society of Chemical Industry

Hemangioma Vascular Endothelial Cells (HVECs) im In-vitro-Modell

Haemangioma is the most common tumour of infancy. Its biological behaviour is one of a benign nature and characterised by a typical biphasic growth pattern. After an initial proliferation during the child's first year of life an involution takes place and usually lasts until the first decade. The expression of cellular and extracellular markers as well as cytokines follows its biphasic growth. In-vitro models reported so far have provided new insights in the tumour's biology and have identified possible targets for pharmacological agents. Our study should enhance the functionality of current in-vitro models in establishing a suspension model of isolated proliferating haemangioma vascular endothelial cells (HVECs). Tissue samples isolated from four haemangiomas (H1-H4) during the proliferation phase were cultivated in four different ways: H1 was cultivated in an MCDB-131 medium whereas for the H2 samples EGM2-MV medium was used. In the H3 series dispase enabled an immediate isolation of pure HVECs from the tissue sample which were cultivated under EMG2-MV medium. In the similarly cultivated H4 series an isolation of cultivated HVECs was enabled by the use of magnetic bead separation which finally led to a suspension model of isolated HVECs. In all four series HVECs were cultivated successfully. Depending on the selected medium different growth rates were observed. The use of dispase and the magnetic bead separation technique resulted in an isolation of cultivated HVECs which was documented in haematoxylin/eosin staining as well as under CD-31 immunohistochemistry. Research on tumour-specific processes as well as possible pharmacological targets necessitates a stable in-vitro model of proliferating HVECs. For our purposes, the described suspension model of HVECs fulfills the requirements of further research on antiproliferation and anti-angiogenesis.

High‐throughput microbial bioassays to screen potential New Zealand functional food ingredients intended to manage the growth of probiotic and pathogenic gut bacteria

SummaryA spectrophotometric bioassay was used to screen selected food ingredients intended for development of functional foods designed to influence the growth of gut bacteria. Dose–response profiles displaying Δgrowth, the magnitude of deviation from growth of controls, were generated for probiotics Lactobacillus reuteri, Lactobacillus rhamnosus, Bifidobacterium lactis and pathogens Escherichia coli, Salmonella Typhimurium and Staphylococcus aureus. Ingredients were manuka honey UMF™20+(dose‐dependently increased probiotics and decreased pathogens); bee pollen (biphasic growth effects against all); Rosehips and BroccoSprouts® (increased all dose‐dependently); blackcurrant oil (little effect) and propolis (inhibited all strains). Ingredients were also bioassayed in pairs to assess desirable or undesirable synergistic interactions. Observed synergies included manuka honey (predominantly desirable); rosehips or BroccoSprouts® (desirable and undesirable); blackcurrant oil (desirable) and propolis (tended towards synergies reinforcing its antimicrobial effects), collectively revealing a complex web of interactions which varied by ingredient and bacterial strain. Manuka honey was particularly effective at influencing gut bacteria. The surprising frequency of undesirable synergistic interactions illustrates the importance of pre‐testing potential ingredient combinations intended for use in functional foods.

Human 2D (index) and 4D (ring) finger lengths and ratios: cross‐sectional data on linear growth patterns, sexual dimorphism and lateral asymmetry from 4 to 60 years of age

Human 2D : 4D ratios (measures of the relative lengths of index and ring fingers) attract considerable research interest because they exhibit sexual dimorphism and are associated with various morphological, physiological and behavioural traits as well as sporting abilities and medical conditions. In an attempt to identify potential confounding factors in such studies, we have examined how relative and absolute digit lengths vary with gender and tested whether they are influenced by age, right-left asymmetry and hand preference. Participants between 4 and 60 years of age were recruited from local educational sites. Hand photocopies and calliper measurement were used to obtain digit lengths. We employed linear regression analysis to examine the growth trajectories of individual digits, analyses of variance to isolate main and interaction effects of age, gender and hand preference, and paired t-tests to identify lateral asymmetries. Both digits exhibited biphasic growth with an early growth phase followed by a stable length phase. Digits in females attained their maximum length about 2.2 years (dextral subjects) or 5.1 years (sinistral subjects) earlier than those in males. Sexual dimorphism in 2D : 4D ratios was apparent by 4 years of age and age changes in ratios depended on gender, side and hand preference. Relative and absolute lengths displayed age, gender, hand-preference and age x gender interaction effects. Lengths tended to be greater in females in younger subjects and greater in males in older subjects. Ratios tended to be greater in sinistral subjects. In dextral subjects, significant lateral asymmetries in 2D lengths were seen at all ages but asymmetries in males and 4D lengths seemed to be age-dependent. We conclude that age, lateral asymmetry and hand preference are potential confounding factors and that future study designs should take account of these as well as other known confounders such as ethnicity, birth order, menstrual cycle phase and sexual preference.

Imagable 4T1 model for the study of late stage breast cancer

BackgroundThe 4T1 mouse mammary tumor cell line is one of only a few breast cancer models with the capacity to metastasize efficiently to sites affected in human breast cancer. Here we describe two 4T1 cell lines modified to facilitate analysis of tumor growth and metastasis and evaluation of gene function in vivo. New information regarding the involvement of innate and acquired immunity in metastasis and other characteristics of the model relevant to its use in the study of late stage breast cancer are reported.MethodsThe lines were engineered for stable expression of firefly luciferase to allow tracking and quantitation of the cells in vivo. Biophotonic imaging was used to characterize growth and metastasis of the lines in vivo and an improved gene expression approach was used to characterize the basis for the metastatic phenotype that was observed.ResultsGrowth of cells at the primary site was biphasic with metastasis detected during the second growth phase 5–6 weeks after introduction of the cells. Regression of growth, which occurred in weeks 3–4, was associated with extensive necrosis and infiltration of leukocytes. Biphasic tumor growth did not occur in BALB/c SCID mice indicating involvement of an acquired immune response in the effect. Hematopoiesis in spleen and liver and elevated levels of circulating leukocytes were observed at week 2 and increased progressively until death at week 6–8. Gene expression analysis revealed an association of several secreted factors including colony stimulatory factors, cytokines and chemokines, acute phase proteins, angiogenesis factors and ECM modifying proteins with the 4T1 metastatic phenotype. Signaling pathways likely to be responsible for production of these factors were also identified.ConclusionThe production of factors that stimulate angiogenesis and ECM modification and induce hematopoiesis, recruitment and activation of leukocytes suggest that 4T1 tumor cells play a more direct role than previously appreciated in orchestrating changes in the tumor environment conducive to tumor cell dissemination and metastasis. The new cell lines will greatly facilitate the study of late stage breast and preclinical assessment of cancer drugs and other therapeutics particularly those targeting immune system effects on tumor metastasis.

TGF-β1 Modulates HGF/SF in Keloid Fibroblast Cell Culture

Objective Abnormal wound healing processes can result in hypertrophic scars and keloids. TGF-β1 and HGF/SF are biphasic growth factor cytokines in physiological and pathophysiological conditions. TGF-β1 has been found to be pivotal in the formation of keloid tissue and therefore neutralising antibodies may allow wound healing without keloid formation. TGF-β1 has been reported to be antagonised by HGF/SF. Some authors have reported that exogenous administration of HGF/SF prevented scar formation. Hence in this study, we targeted TGF-β1 and determined the levels of HGF/SF in fibroblast cell culture. Methods Keloid tissue was taken from 7 patients while another 7 patients with mature non-hypertrophic scar served as controls. All tissues were cultured and fibroblast cultures were used for further experiments. TGF-β1 antisense was administered at 3 and 6 μmol/ml and HGF/SF levels were determined after 16, 24 and 48 hours of incubation. Results The levels of HGF/SF showed significant differences after incubation with antisense oligonucleotides. The increasing antisense levels resulted in increased HGF/SF levels (up to 87.66pg/ml after 48 hours of incubation). Conclusions In conclusion, targeting TGF-β1 resulted in significantly increased levels of HGF/SF. The clinical relevance could include the use of locally administered HGF/SF in protein or gene form to minimise keloid formation. Nevertheless, wound healing is the result of many interacting cytokines and therefore neutralising or targeting one protein could result in no significant effect.

Biphasic growth in fish II: Empirical assessment

In [Quince, et al., 2008. Biphasic growth in fish I: Theoretical foundations. J. Theor. Biol., doi: 10.1016/j.jtbi.2008.05.029], we developed a set of biphasic somatic growth models, where maturation is accompanied by a deceleration of growth due to allocation of energy to reproduction. Here, we use growth data from both hatchery-raised and wild populations of a large freshwater fish (lake trout, Salvelinus namaycush) to test these models. We show that a generic biphasic model provides a better fit to these data than the von Bertalanffy model. We show that the observed deceleration of somatic growth in females varies directly with gonad weight at spawning, with observed egg volumes roughly 50% of the egg volumes predicted under the unrealistic assumption of perfectly efficient energy transfer from somatic lipids to egg lipids. We develop a Bayesian procedure to jointly fit a biphasic model to observed growth and maturity data. We show that two variants of the generic biphasic model, both of which assume that annual allocation to reproduction is adjusted to maximise lifetime reproductive output, provide complementary fits to wild population data: maturation time and early adult growth are best described by a model with no constraints on annual reproductive investment, while the growth of older fish is best described by a model that is constrained so that the ratio of gonad size to somatic weight ( g) is fixed. This behaviour is consistent with the additional observation that g increases with size and age among younger, smaller breeding females but reaches a plateau among older, larger females. We then fit both of these optimal models to growth and maturation data from nineteen wild populations to generate population-specific estimates of ‘adapted mortality’ rate: the adult mortality consistent with observed growth and maturation schedules, given that both schedules are adapted to maximise lifetime reproductive output. We show that these estimates are strongly correlated with independent estimates of the adult mortality experienced by these populations.

Biphasic growth in fish I: Theoretical foundations

We develop the theory of biphasic somatic growth in fish using models based on the distinction between pre- and post-maturation growth and an explicit description of energy allocation within a growing season. We define a ‘generic biphasic’ (GB) model that assumes post-maturation growth has a von Bertalanffy (vB) form. For this model we derive an explicit expression for the gonad weight/somatic weight ratio ( g) which may either remain fixed or vary with size. Optimal biphasic models are then developed with reproductive strategies that maximise lifetime reproductive output. We consider two optimal growth models. In the first (fixed g optimal), gonad weight is constrained to be proportional to somatic weight. In the second (variable g optimal) model, allocation to reproduction is unconstrained and g increases with size. For the first of these two models, adult growth in a scaled measure of length has the exact vB form. When there are no constraints on allocation, growth is vB to a very good approximation. In both models, pre-maturation growth is linear. In a companion paper we use growth data from lake trout ( Salvelinus namaycush) to test the bioenergetics assumptions used to develop these models, and demonstrate that they have advantages over the vB model, both in quality of fit, and in the information contained in the fitted parameters.

Modelling the stress inducing biphasic growth and pediocin production by Pediococcus acidilactici NRRL B-5627 in re-alkalized fed-batch cultures

Five re-alkalized fed-batch cultures of Pediococcus acidilactici NRRL B-5627 were carried out in culture media prepared with mussel processing wastes (MPWs) and whey under different fermentation conditions. The shift from homolactic to mixed acid product formation and the biphasic kinetics observed for cell growth, nitrogen consumption and pediocin production were the most noteworthy observations of these cultures. For a better understanding of the culture dynamics and for a suitable description of the bacteriocin production system, an unstructured mathematical model based on the two phases of nitrogen consumption was developed. The model was expressed in terms of biomass, product accumulation and substrate utilization. Excellent agreements between model predictions and experimental data were achieved in the five re-alkalized fed-batch cultures and a reasonable description for each parameter in each growth phase was provided by the model. Using published experimental data by other researchers, model agreement was also found for the growth of Ped. acidilactici NRRL B-5627 in a repeatedly re-alkalized culture in a synthetic culture medium. The developed model appears to be useful for the design, scale-up, control and optimization of the production of potentially probiotic cultures and bacteriocins.

Transforming Growth Factor-β1-Antisense Modulates the Expression of Hepatocyte Growth Factor/Scatter Factor in Keloid Fibroblast Cell Culture

Abnormal wound healing processes can result in hypertrophic scars and keloids. Transforming growth factor-beta1 (TGF-beta1) and hepatocyte growth factor/scatter factor (HGF/SF) are biphasic growth factor cytokines in physiologic and pathophysiologic conditions. Findings have shown TGF-beta1 to be pivotal in the formation of keloid tissue. Therefore, neutralizing antibodies may allow wound healing without keloid formation. As reported, TGF-beta1 is antagonized by HGF/SF. Some authors have reported that exogenous administration of HGF/SF prevented scar formation. Hence, this study targeted TGF-beta1 and determined the levels of HGF/SF in fibroblast cell culture. Keloid tissue was taken from seven patients. Another seven patients with mature nonhypertrophic scar served as controls. All tissues were cultured, and fibroblast cultures were used for further experiments. The TGF-beta1 antisense was administered at 3 and 6 micromol/ml, and HGF/SF levels were determined after 16, 24, and 48 h of incubation. The levels of HGF/SF showed significant differences after incubation with antisense oligonucleotides. The increasing antisense levels resulted in increased HGF/SF levels (up to 87.66 pg/ml after 48 h of incubation). In conclusion, targeting TGF-beta1 resulted in significantly increased levels of HGF/SF. The clinical relevance could include the use of locally administered HGF/SF in protein or gene form to minimize formation of keloids. Nevertheless, wound healing is the result of many interacting cytokines, so neutralizing or targeting one protein could result in no significant effect.

An investigation of biphasic growth kinetics for Phanerochaete chrysosporium (BKMF-1767) immobilised in a membrane gradostat reactor using flow-cells

A novel membrane gradostat reactor (MGR) was patented in 1999. This MGR is used for the continuous production of secondary metabolites, such as lignin peroxidase and manganese peroxidase, from an immobilised biofilm of Phanerochaete chrysosporium, in response to nitrogen starvation. Extensive research has been done previously on the biochemistry and the enzymatic activities of this fungus, but very little information is available on this fungus’ growth kinetics and nutrient consumption, within a continuously operated MGR system. It was the purpose of this study to identify the biofilm growth phases and to quantify the growth kinetics and nutrient consumption of an immobilised biofilm of P. chrysosporium (BKMF-1767) using single-capillary flow-cell MGR's, operated under different spore concentrations and airflow rates. Biofilm thickness increased with an increase in both spore concentration and airflow rate. Biphasic growth (first and second exponential growth phases, separated by a short intermediate lag phase) was demonstrated. For the first exponential growth phase, the biofilm thickness increase rate ( k f) ranged between 0.07 and 0.1 h −1 and for the second exponential growth phase the growth slowed down to between 0.015 and 0.05 h −1. The ammonium depletion of 96–99% corresponded to the time of the intermediate lag phase. At the end of the first exponential growth phase, the glucose depletion was approximately 13%, compared to 24% during the second exponential growth phase. For this system, the intermediate lag phase occurred in response to the ammonium depletion and not glucose depletion. The fungal growth was accompanied by pH acidification, attributed to NH 4 +/H + exchange, only up to the time of ammonium depletion. The determination of the biofilm thickness increase rate, k f, for biphasic growth, in relation to glucose and ammonium consumption, for within a MGR system, was not previously reported.

Ethanol Catabolism in Corynebacterium glutamicum

Corynebacterium glutamicum grows on a variety of carbohydrates and organic acids as single or combined sources of carbon and energy. Here we show the ability of C. glutamicum to grow on ethanol with growth rates up to 0.24 h^–1 and biomass yields up to 0.47 g dry weight (g ethanol)^–1. Mutants of C. glutamicum deficient in phosphotransacetylase (PTA), isocitrate lyase (ICL) and malate synthase (MS) were unable to grow on ethanol, indicating that acetate activation and the glyoxylate cycle are essential for utilization of this substrate. In accordance, the expression profile of ethanol-grown C. glutamicum cells compared to that of glucose-grown cells revealed an increased expression of genes encoding acetate kinase (AK), PTA, ICL and MS. Furthermore, the specific activities of these four enzymes as well as those of alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH) were found to be high in ethanol-grown and low in glucose-grown cells. Growth of C. glutamicum on a mixture of glucose and ethanol led to a biphasic growth behavior, which was due to the sequential utilization of glucose before ethanol. Accordingly, the specific activities of ADH, ALDH, AK, PTA, ICL and MS in cells grown in medium containing both substrates were as low as in glucose-grown cells in the first growth phase, but increased 5- to 100-fold during the second growth phase. The results indicate that ethanol catabolism in C. glutamicum is subject to carbon source-dependent regulation, i.e., to a carbon catabolite control.

Regulatory Overlap and Functional Redundancy amongBacillus subtilisExtracytoplasmic Function σ Factors

Bacillus subtilis encodes seven extracytoplasmic function (ECF) sigma factors that regulate partially overlapping regulons related to cell envelope homeostasis and antibiotic resistance. Here, we investigated their physiological role by constructing a mutant set of single, double, triple, and quadruple ECF sigma factor deletions in the undomesticated B. subtilis strain NCIB3610. This mutant set was subsequently screened for defects in motility, multicellular differentiation, and sensitivity to more than 200 chemicals by using Phenotype MicroArrays. A quadruple mutant strain, harboring deletions of the sigV, sigY, sigZ, and ylaC gene, behaved indistinguishably from the wild-type strain, indicative of either regulatory redundancy or very specific functions of these four ECF sigma factors. In contrast, a triple mutant, inactivated for the sigM, sigW, and sigX genes (but none of the corresponding double mutants), showed a biphasic growth behavior and a complete loss of multicellular differentiation, as judged by both colony formation and the inability to form a pellicle. This triple mutant also displayed a greatly increased sensitivity to detergents and several cell wall antibiotics including beta-lactams, polymyxin B, and d-cycloserine. In several cases, these antibiotic-sensitive phenotypes are significantly enhanced in the triple mutant strain relative to strains lacking only one or two sigma factors.