Carbon Source Starvation Research Articles

The combined effect of carbon starvation and exogenous riboflavin accelerated the Pseudomonas aeruginosa-induced nickel corrosion

The primary objective of this study is to elucidate the synergistic effect of an exogenous redox mediator and carbon starvation on the microbiologically influenced corrosion (MIC) of metal nickel (Ni) by nitrate reducing Pseudomonas aeruginosa. Carbon source (CS) starvation markedly accelerates Ni MIC by P. aeruginosa. Moreover, the addition of exogenous riboflavin significantly decreases the corrosion resistance of Ni. The MIC rate of Ni (based on corrosion loss volume) is ranked as: 10 % CS level + riboflavin > 100 % CS level + riboflavin > 10 % CS level > 100 % CS level. Notably, starved P. aeruginosa biofilm demonstrates greater aggressiveness in contributing to the initiation of surface pitting on Ni. Under CS deficiency (10 % CS level) in the presence of riboflavin, the deepest Ni pits reach a maximum depth of 11.2 μm, and the corrosion current density (icorr) peak at approximately 1.35 × 10−5 A·cm−2, representing a 2.6-fold increase compared to the full-strength media (5.25 × 10−6 A·cm−2). For the 10 % CS and 100 % CS media, the addition of exogenous riboflavin increases the Ni MIC rate by 3.5-fold and 2.9-fold, respectively. Riboflavin has been found to significantly accelerate corrosion, with its augmentation effect on Ni MIC increasing as the CS level decreases. Overall, riboflavin promotes electron transfer from Ni to P. aeruginosa, thus accelerating Ni MIC.

Effects of carbon source starvation and riboflavin addition on selective corrosion of welded joint by Desulfovibrio vulgaris

This study systematically explores the impact of carbon source starvation (CCS) and the addition of riboflavin on the corrosion of X80 welded joints by Desulfovibrio vulgaris. The results showed that the Desulfovibrio vulgaris corrosion of the welded joint was apparently selective under the independent action of CCS or riboflavin addition, while the selectivity distinctly decreased under their combined action. More grain boundaries and higher proportion of the low-angle grain boundaries in the base metal and welding zone were the reasons for the selective corrosion. The attachment behavior of the Desulfovibrio vulgaris cells was responsible for the decreasing of the selectivity.

Starvation combined with constant anode potential triggers intracellular electron storage in electro-active biofilms

The accumulation of electrons in the form of Extracellular Polymeric Substances (EPS) and poly-hydroxyalkanoates (PHA) has been studied in anaerobic processes by adjusting the access of microorganisms to the electron donor and final electron acceptor. In Bio-electrochemical systems (BESs), intermittent anode potential regimes have also recently been used to study electron storage in anodic electro-active biofilms (EABfs), but the effect of electron donor feeding mode on electron storage has not been explored. Therefore, in this study, the accumulation of electrons in the form of EPS and PHA was studied as a function of the operating conditions. EABfs were grown under both constant and intermittent anode potential regimes and fed with acetate (electron donor) continuously or in batch. Confocal Laser Scanning Microscopy (CLSM) and Fourier-Transform Infrared Spectroscopy (FTIR) were used to assess electron storage. The range of Coulombic efficiencies, from 25 to 82%, and the biomass yields, between 10 and 20%, indicate that storage could have been an alternative electron consuming process. From image processing, a 0.92 pixel ratio of poly-hydroxybutyrate (PHB) and amount of cells was found in the batch fed EABf grown under a constant anode potential. This storage was linked to the presence of living Geobacter and shows that energy gain and carbon source starvation were the triggers for intracellular electron storage. The highest EPS content (extracellular storage) was observed in the continuously fed EABf under an intermittent anode potential, showing that constant access to electron donor and intermittent access to the electron acceptor leads to the formation of EPS from the excess energy gained. Tailoring operating conditions can thus steer the microbial community and result in a trained EABf to perform a desired biological conversion, which can be beneficial for a more efficient and optimized BES.

The Nitrate-Dependent Impact of Carbon Source Starvation on EH40 Steel Corrosion Induced by the Coexistence of Desulfovibrio vulgaris and Pseudomonas aeruginosa

Carbon source starvation can promote steel corrosion in the presence of a pure culture through extracellular electron transfer (EET). However, the impact of carbon source starvation on corrosion induced by mixed strains is still unknown. This work investigated the impact of carbon source starvation on EH40 steel corrosion in the presence of Desulfovibrio vulgaris and Pseudomonas aeruginosa, typical species of sulfate- and nitrate-reducing bacteria. It was found that the impact of carbon source starvation on corrosion depended on nitrate addition. When nitrate (5 g∙L−1 NaNO3) was not added, the corrosion was promoted by carbon source starvation. However, the corrosion was initially promoted by carbon source starvation, but later inhibited with nitrate addition. The corrosion behaviors in different systems were closely related to different numbers of the strains in biofilms and their metabolic activities, and the mechanisms were revealed.

Microbiologically influenced corrosion of titanium by Desulfovibrio vulgaris biofilm under organic carbon starvation

Desulfovibrio vulgaris biofilm was pre-grown on Ti coupons for 7 d and then the biofilm covered coupons were incubated again with fresh culture media with 10 % (reduced) and 100 % (normal) carbon source levels, respectively. After the pre-growth, sessile D. vulgaris cell count reached 107 cells/cm2. The sessile cell counts were 2 × 107 and 4.2 × 107 cells/cm2 for 10 % and 100 % carbon sources, respectively after the subsequent 7 d starvation test. The maximum pit depth after the 7 d pre-growth was 4.7 µm. After the additional 7 d of the starvation test, the maximum pit depth increased to 5.1 µm for 100 % carbon source vs 6.2 µm for 10 % carbon source. Corrosion current density (icorr) from potentiodynamic polarization data at the end of the 7 d starvation test for 10 % carbon source was more than 3 times of that for 100 % carbon source, despite a reduced sessile cell count with 10 % carbon source. The polarization resistance (Rp) started to decrease within minutes after 20 ppm (w/w) riboflavin (electron mediator) injection. The carbon starvation data and riboflavin corrosion acceleration data both suggested that D. vulgaris utilized elemental Ti as an electron source to replace carbon source as the electron donor during carbon source starvation.

Accelerated sulfate reducing bacteria corrosion of X80 pipeline steel welded joints under organic carbon source starvation

Sulfate-reducing bacteria (SRB) corrosion of X80 steel welded joint under organic carbon source starvation was investigated in the paper. The results showed that the number of planktonic cells is much less than that of sessile cells after 720 h immersion. The number of sessile cells in the base metal (BM) in the medium with 1% carbon source is the largest. Starving SRB cells accelerated simultaneously the uniform corrosion and localized corrosion of the welded joints, and the acceleration effect on the latter was much higher than that of the former. In all mediums, the density and average depth of pits in the BM and weld zone (WZ) were much larger than those in the heat affected zone (HAZ). SRB corrosion of the welded joint was strongly selective, and organic carbon source starvation further enhanced the selectivity.

Carbon Source Starvation of a Sulfate-Reducing Bacterium–Elevated MIC Deterioration of Tensile Strength and Strain of X80 Pipeline Steel

It is known that starved sulfate-reducing bacterial biofilms corrode carbon steel more aggressively because they use electrons from elemental iron oxidation as an alternative source of energy. This work used carbon source starvation to vary MIC (microbiologically influenced corrosion) severity for studying subsequent MIC impacts on the degradation of X80 carbon steel mechanical properties. X80 square coupons and dogbone coupons were immersed in ATCC 1249 culture medium (200 ml in 450-ml anaerobic bottles) inoculated with Desulfovibrio vulgaris for 3-day pre-growth and then for an additional 14 days in fresh media with adjusted carbon source levels for starvation testing. After the starvation test, the sessile cell counts (cells/cm2) on the dogbone coupons in the bottles with carbon source levels of 0, 10, 50, and 100% (vs that in the full-strength medium) were 8.1 × 106, 3.2 × 107, 8.3 × 107, and 1.3 × 108, respectively. The pit depths from the X80 dogbone coupons were 1.9 μm (0%), 4.9 μm (10%), 9.1 μm (50%), and 6.4 μm (100%). The corresponding weight losses (mg/cm2) from the square coupons were 1.9 (0%), 3.3 (10%), 4.4 (50%), and 3.7 (100%). The 50% carbon source level had the combination of carbon starvation without suffering too much sessile cell loss. Thus, both its pit depth and weight loss were the highest. The electrochemical tests corroborated the pit depth and weight loss trends. The tensile tests of the dogbone coupons after the starvation incubation indicated that sulfate-reducing bacteria (SRB) made X80 more brittle and weaker. Compared with the fresh (no-SRB-exposure) X80 dogbone coupon’s ultimate tensile strain of 13.6% and ultimate tensile stress of 860 MPa, the 50% carbon source level led to the lowest ultimate tensile strain of 10.3% (24% loss when compared with the fresh dogbone) and ultimate tensile stress of 672 MPa (22% loss). The 100% carbon source level had a smaller loss in ultimate tensile strain than the 50% carbon source level, followed by 10% and then 0%. Moreover, the 100% carbon source level had a smaller loss in ultimate tensile strength than the 50%, followed by 10% and 0% in a tie. This outcome shows that even in the 17-day short-term test, significant degradation of the mechanical properties occurred and more severe MIC pitting caused more severe degradation.

Extracellular electron transfer in microbial biocorrosion

Biocorrosion by microbial biofilms is also termed microbiologically influenced corrosion (MIC). For many decades in MIC research, people focused on corrosive metabolites. In the past decade, researchers started to apply bioenergetics to MIC science research. They realized that extracellular oxidation of a metal can supply electrons for microbial respiration, which causes MIC. Because these electrons must be transported to the cytoplasm via extracellular electron transfer (EET), this kind of MIC is called EET-MIC, which is different from metabolite-MIC (M-MIC). Advances have been made to decipher inward EET involved in MIC. Carbon source starvation and electron mediator acceleration have been used to study impact of EET on MIC. More recently, manipulations of electron mediator-related genes have been used to elucidate EET in MIC. EET in energy metabolism in microbiology and EET for MIC are intertwined. Well-established corrosion research tools, especially electrochemical methods that are highly sensitive, are useful for microbiologists to study EET. • Extracellular electron transfer (EET) is involved in one key type of biocorrosion. • Direct electron transfer and mediated electron transfer are found in biocorrosion. • Experimental evidence for different types of EET in biocorrosion is discussed. • Newest proofs of EET in biocorrosion come from manipulations of EET-related genes. • Perspectives on EET importance in biocorrosion and future research are provided.

Decreased expression of LRA4, a key gene involved in rhamnose metabolism, caused up-regulated expression of the genes in this pathway and autophagy in Pichia pastoris

In a previous study, we developed Pichia pastoris GS115m, an engineered strain with decreased expression of one key gene, LRA4, in rhamnose metabolism. P. pastoris GS115m/LacB was subsequently constructed via introducing a β-galactosidase gene, LacB, under the control of rhamnose-inducible PLRA3 into P. pastoris GS115m. P. pastoris GS115m/LacB greatly improved recombinant protein production relative to the parental strain (P. pastoris GS115/LacB). In the present study, transcriptomes of P. pastoris GS115m/LacB and P. pastoris GS115/LacB grown in YPR medium were analyzed. P. pastoris GS115m/LacB was found to suffer from the mild carbon source starvation. To attenuate the starvation stress, P. pastoris GS115m/LacB attempted to enhance rhamnose metabolism by elevating the transcription levels of rhamnose-utilization genes LRA1-3 and RhaR. The transcription level of LacB under the control of PLRA3 thereby increased, resulting in the improved production of recombinant protein in P. pastoris GS115m/LacB. It was also revealed that P. pastoris GS115m/LacB cells coped with carbon starvation mostly via autophagy.

Effects of biomass and environmental factors on nitrogen removal performance and community structure of an anammox immobilized filler

In order to reduce the loss of anaerobic ammonia oxidation (anammox) sludge and stabilize the reaction microenvironment, polyvinyl alcohol - polypropylene (PVA-PP) was used to encapsulate anammox bacteria on a filler. The influence of different inoculation amounts (2, 4, 6 and 8%) on the overall nitrogen removal process was first compared and then the anammox characteristics of the immobilized filler under the influence of different environmental factors were evaluated through batch experiments. The results show that the biomass only affected the growth rate of the activity during the logarithmic phase, while the total nitrogen removal rate (NRR) tended to be similar after 99 d of culture. The NRR reached 1.83 kg·(m3·d)-1 on day 140, which was 9.4 times that of suspended sludge before encapsulation, and the structure of embedding filler was complete without shedding. Scanning electron microscopy (SEM) showed that the internal porous network structure formed channels and a large number of anammox bacteria were observed around. Microbial community analysis of the 16S rDNA gene showed that the diversity was maintained in the entrapped carrier. Furthermore, the effective enrichment of the anammox functional bacteria Candidatus Kuenenia (AF375995.1) increarsed from 11.06% to 32.55%. The PVA-PP immobilized filler fit well with the biological nitrogen removal kinetic model and could also achieve coupling of anammox and denitrification. The inhibition effect of the organic carbon source interference and starvation on anammox bacteria was significantly weakened.

Accelerated corrosion of pipeline steel in the presence of Desulfovibrio desulfuricans biofilm due to carbon source deprivation in CO2 saturated medium.

The chemistry of bacterial biofilms as well as the nutritional composition of culture environments may differ at any time within a growth process, especially for SRB consortia within oil wells with limited carbon sources. In the oilfield, the presence of SRB biofilms on surfaces of steel substrates leads to microbiologically influenced corrosion and compromised material integrity. In this work, the survival of SRB cells and their impact on the pipeline steel corrosion within simulated CO2-saturated oilfield-produced water with different concentrations of organic carbon source have been investigated. Cell counts reduced with the level of carbon source reduction (CSR) after incubation but more sessile cells survived at 80% CSR (moderate carbon starvation) compared to 100% CSR (extreme carbon starvation). The energy needed for cellular survival as well as biological support toward MIC could have been harnessed by a combination of extracellular Feo oxidation and intracellular sulfate reduction even after carbon source starvation. Severe anodic steel dissolution was observed at the end of the culture period within the simulated CO2-saturated oilfield-produced water, and this is attributed to SRB-led MIC and CO2 corrosion. Pipeline steel corroded more when cultured within 80% CSR compared to the medium with both lactate and citrate. Steel substrate corroded less with 100% CSR due to severely weakened SRB biofilms from nutrient deprivation.

Inhibiting Biocorrosion of Pipeline Steel in the Presence of Zinc Molybdate Nanocrystals within a CO2 Saturated Desulfovibrio Desulfuricans bacterial Culture Under Carbon Source Deprivation

Even with limited organic carbon sources in oilfields, the presence of sulphate reducing bacteria (SRB) intensifies microbiologically influenced corrosion (MIC), consequently leading to compromised material integrity. On pipeline steel substrates with active biofilms, Feo is subsequently utilized as an alternative donor by SRBs during energy metabolism. In this work, the survival of Desulfovibrio desulfuricans (ATCC 27774) SRB cells and their impact on the pipeline steel (API 5L X70) corrosion within simulated CO2-saturated oilfield-produced water with different concentrations of organic carbon source have been investigated. Cell counts reduced with the level of carbon source reduction after incubation, but more cells survived at moderate carbon starvation compared to extreme conditions. To combat MIC, we have introduced different concentrations of zinc molybdate (ZnM) crystals against bacterial growth, synthesized from a new chemical route. The rate of MIC reduces more than 80 times in the presence of ZnM crystals under anaerobic conditions, and this has been attributed to the cellular growth inhibitive effect of ZnM. The extent of SRB colonization of steel was monitored within duration of study using confocal laser scanning microscopy after staining with appropriate Live/Dead dyes. Steel biocorrosion mechanism is elucidated by means of electrochemical impedance spectroscopy, potentiodynamic polarization and surface analyses. Adhering corrosion products on steel in the presence of D. desulfuricans biofilm are predominantly FeO films and FeS/MnS aggregates; this has been confirmed by X-ray photoelectron spectroscopy. Severe anodic steel dissolution is observed on steel within the test culture without ZnM, and this is attributed to SRB-led MIC and CO2 corrosion. Here, the energy needed for cellular survival was harnessed by a combination of Feo oxidation and sulfate reduction even after carbon source starvation. The degree of biocorrosion inhibition increases with ZnM crystal concentration and as more bacterial cells die off within the culture media.

Electrochemical investigation of increased carbon steel corrosion via extracellular electron transfer by a sulfate reducing bacterium under carbon source starvation

Microbiologically influenced corrosion (MIC) of carbon steel by sulfate reducing bacterium (SRB) Desulfovibrio vulgaris under organic carbon starvation was investigated using electrochemical methods to support weight loss and pitting data. 20% carbon source led to the highest weight loss (6.6 mg/cm2), while 100% had the lowest (3.3 mg/cm2) after 10 days. Linear polarization resistance and electrochemical impedance spectrometry data confirmed the weight loss and pitting data trends. The data in this work support the theory that carbon steel corrosion by SRB is due to electron harvest from extracellular iron oxidation by SRB, which belongs to extracellular electron transfer MIC (EET-MIC).

Regulation and Physiology of Autophagy Induced by Glucose Starvation “The role of autophagy for the degradation of intracellular mannosyl glycan in yeast”

Autophagy is a conserved degradation pathway driven by the sequestration of various cytoplasmic components into the vacuoles/lysosomes in eukaryotic cells. Autophagy is known to play an important role in cellular homeostasis by eliminating excess/damaged organelles or by providing amino acids during nutrition starvation. Several studies have suggested that dysregulation of autophagy causes physiological dysfunction in both yeast and mammals. It has been reported that the magnitude of autophagy is strongly enhanced by starvation of various nutrition sources, such as nitrogen, carbon and phosphorus. However, the regulatory mechanism and physiology of autophagy induced by each nutritional shortage—with the exception of nitrogen starvation—have been largely unclear. In this review, I focus on recent studies of the regulation and physiology of autophagy induced by glucose (or carbon source) starvation, as well as the historical background of autophagy study in Saccharomyces cerevisiae. Our recent findings indicate that autophagy plays a role in facilitating degradation of the intracellular mannosyl glycan during glucose starvation in budding yeast.

Toward a better understanding of microbiologically influenced corrosion caused by sulfate reducing bacteria

Sulfate reducing bacteria (SRB) are often the culprits of microbiologically influenced corrosion (MIC) in anoxic environments because sulfate is a ubiquitous oxidant. MIC of carbon steel caused by SRB is the most intensively investigated topic in MIC because of its practical importance. It is also because biogenic sulfides complicate mechanistic SRB MIC studies, making SRB MIC of carbon steel is a long-lasting topic that has generated considerable confusions. It is expedient to think that biogenic H2S secreted by SRB acidifies the broth because it is an acid gas. However, this is not true because endogenous H2S gets its H+ from organic carbon oxidation and the fluid itself in the first place rather than an external source. Many people believe that biogenic H2S is responsible for SRB MIC of carbon steel. However, in recent years, well designed mechanistic studies provided evidence that contradicts this misconception. Experimental data have shown that cathodic electron harvest by an SRB biofilm from elemental iron via extracellular electron transfer (EET) for energy production by SRB is the primary cause. It has been demonstrated that when a mature SRB biofilm is subjected to carbon source starvation, it switches to elemental iron as an electron source and becomes more corrosive. It is anticipated that manipulations of EET related genes will provide genetic-level evidence to support the biocathode theory in the future. This kind of new advances will likely lead to new gene probes or transcriptomics tools for detecting corrosive SRB strains that possess high EET capabilities.

Corrosion of X80 pipeline steel under sulfate-reducing bacterium biofilms in simulated CO2-saturated oilfield produced water with carbon source starvation

Corrosion of X80 pipeline steel under sulfate-reducing bacterium (SRB) biofilms, which formed in a culture medium at different times, in a simulated CO2-saturated oilfield produced water was investigated. Both planktonic and sessile SRB cells survived after 21 days of immersion in the water under carbon source starvation. The biofilms pre-cultured with a longer time increased the corrosion rate of the steel. At 37 °C, it took about 4 days for SRB to grow and then participate in the steel corrosion. The SRB also facilitated localized corrosion. The SRB biofilm, once deactivated, would no longer affect the steel corrosion.

Effect of Iron Oxidizing Bacteria Biofilm on Corrosion Inhibition of Imidazoline Derivative in CO2-Containing Oilfield Produced Water with Organic Carbon Source Starvation

In this work, corrosion of a Q235 carbon steel in CO2-containing oilfield produced water in the presence of iron oxidizing bacteria (IOB) with organic carbon source starvation and the inhibiting performance of imidazoline derivative were investigated by weight loss, electrochemical measurements and surface analysis techniques. Results show that iron oxidizing bacteria (IOB) could survive well in the aqueous environments with organic carbon source starvation. Corrosion of the steel occurred under the IOB biofilm. Both the planktonic and sessile IOB cell counts after 14 days of testing were related to the biofilm incubation time. The corrosion rate of the steel covered with 7-day IOB biofilm was lowest suggesting that this biofilm had the weakest corrosivity in the test solution. The inhibition performance of the inhibitor was affected by the IOB biofilm formed on steel surface. There was a higher inhibition efficiency of the inhibitor, when the steel was covered with a 2-day IOB biofilm due to less IOB biofilm formed on the steel.

Microbiologically influenced corrosion of C1018 carbon steel by nitrate reducing Pseudomonas aeruginosa biofilm under organic carbon starvation

This work showed that a wild-type Pseudomonas aeruginosa (PAO1) grown as a nitrate reducing bacterium biofilm on C1018 carbon steel was more corrosive under organic carbon source starvation. P. aeruginosa biofilms were pre-grown for 2days to achieve maturity before the culture media were changed to fresh culture media with 100% (as in the standard medium), 10%, and 0% organic carbons for subsequent 7-day incubation. Biofilms with 100%, 10%, and 0% organic carbons caused maximum pit depths of 5.4μm, 10.6μm, and 17.0μm, respectively. Weight loss, linear polarization resistance and electrochemical impedance spectroscopy data corroborated the pitting data.

Starved Escherichia coli preserve reducing power under nitric oxide stress

Nitric oxide (NO) detoxification enzymes, such as NO dioxygenase (NOD) and NO reductase (NOR), are important to the virulence of numerous bacteria. Pathogens use these defense systems to ward off immune-generated NO, and they do so in environments that contain additional stressors, such as reactive oxygen species, nutrient deprivation, and acid stress. NOD and NOR both use reducing equivalents to metabolically deactivate NO, which suggests that nutrient deprivation could negatively impact their functionality. To explore the relationship between NO detoxification and nutrient deprivation, we examined the ability of Escherichia coli to detoxify NO under different levels of carbon source availability in aerobic cultures. We observed failure of NO detoxification under both carbon source limitation and starvation, and those failures could have arisen from inabilities to synthesize Hmp (NOD of E. coli) and/or supply it with sufficient NADH (preferred electron donor). We found that when limited quantities of carbon source were provided, NO detoxification failed due to insufficient NADH, whereas starvation prevented Hmp synthesis, which enabled cells to maintain their NADH levels. This maintenance of NADH levels under starvation was confirmed to be dependent on the absence of Hmp. Intriguingly, these data show that under NO stress, carbon-starved E. coli are better positioned with regard to reducing power to cope with other stresses than cells that had consumed an exhaustible amount of carbon.

Compartmentalized microchannel array for high-throughput analysis of single cell polarized growth and dynamics.

Interrogating polarized growth is technologically challenging due to extensive cellular branching and uncontrollable environmental conditions in conventional assays. Here we present a robust and high-performance microfluidic system that enables observations of polarized growth with enhanced temporal and spatial control over prolonged periods. The system has built-in tunability and versatility to accommodate a variety of scientific applications requiring precisely controlled environments. Using the model filamentous fungus, Neurospora crassa, our microfluidic system enabled direct visualization and analysis of cellular heterogeneity in a clonal fungal cell population, nuclear distribution and dynamics at the subhyphal level, and quantitative dynamics of gene expression with single hyphal compartment resolution in response to carbon source starvation and exchange. Although the microfluidic device is demonstrated on filamentous fungi, the technology is immediately extensible to a wide array of other biosystems that exhibit similar polarized cell growth, with applications ranging from bioenergy production to human health.