No Apparent Costs for Facultative Antibiotic Production by the Soil Bacterium Pseudomonas fluorescens Pf0-1

Background: Many soil-inhabiting bacteria are known to produce secondary metabolites that can suppress microorganisms competing for the same resources. The production of antimicrobial compounds is expected to incur fitness costs for the producing bacteria. Such costs form the basis for models on the co-existence of antibiotic-producing and non-antibiotic producing strains. However, so far studies quantifying the costs of antibiotic production by bacteria are scarce. The current study reports on possible costs, for antibiotic production by Pseudomonas fluorescens Pf0-1, a soil bacterium that is induced to produce a broad-spectrum antibiotic when it is confronted with non-related bacterial competitors or supernatants of their cultures. Methodology and Principal Findings: We measured the possible cost of antibiotic production for Pseudomonas fluorescens Pf0-1 by monitoring changes in growth rate with and without induction of antibiotic production by supernatant of a bacterial competitor, namely Pedobacter sp.. Experiments were performed in liquid as well as on semi-solid media under nutrient-limited conditions that are expected to most clearly reveal fitness costs. Our results did not reveal any significant costs for production of antibiotics by Pseudomonas fluorescens Pf0-1. Comparison of growth rates of the antibioticproducing wild-type cells with those of non-antibiotic producing mutants did not reveal costs of antibiotic production either. Significance: Based on our findings we propose that the facultative production of antibiotics might not be selected to mitigate metabolic costs, but instead might be advantageous because it limits the risk of competitors evolving resistance, or even the risk of competitors feeding on the compounds produced.

Antifungal rhizosphere bacteria can increase as response to the presence of saprotrophic fungi

Acknowledgments: Funding was provided by the Netherlands Organisation for Scientific Research (NWO) in the form of a personal Veni grant to A.v.d.W. This is publication number 5923 of the NIOO-KNAW Netherlands Institute of Ecology. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

The Pathophysiology ofProtein-Overload Proteinur a

Alterations in glomerular function and structure were studied in protein-overload nephrosis in the rat induced by intraperitoneal administration of bovine serum albumin (BSA). Fractional clearance (C/GFR) studies using inulin and tracer proteins of different molecular size and charge revealed in proteinuric rats 1) unchanged glomerular filtration rate and renal plasma flow; 2) a 34-fold increase in C/GFR of rat serum albumin, reaching values similar to BSA; 3) a 2-fold increase in C/GFR for anionic horse radish peroxidase (HRP), but normal values for neutral and cationic HRP, and 4) an 11-and 3-fold increase for heter-THE GLOMERULAR capillary wall (GCW) constitutes a semipermeable, size-and charge-selective filter between the glomerular capillary lumen and the urinary space." 2 Under normal conditions, the ultrafiltrate is virtually devoid ofproteins. Increased permeability to plasma proteins may be caused by a number ofimmunopathologic, toxic, or hemodynamic events leading to damage ofthe endothelial and/or epithelial cells and disruption of the glomerular basement membrane (GBM).3'4 Increased passage of proteins from the capillary lumen to the urinary space has also been observed in man and in laboratory animals after parenteral administration of high amounts of proteins.5-26 Studies on experimental models of proteinoverload proteinuria have shown that increased transcapillary movement of proteins causes degenerative changes ofglomerular epithelial cells characterized by swelling, vacuolization, increased reabsorption droplets, loss of foot processes, and lifting from the underlying GBM.'1"220 Recent studies have reported on functional and structural glomerular alterations in rat models of protein-overload proteinuria, providing conflicting evidence with regard to changes in sizeand charge-selective properties ofthe GCW. In BSAinduced proteinuria sieving curves of neutral dextrans were found to be normal, suggestive ofan intact sieving filter.23 In contrast, in the same model inFrom the Departments ofPathology and Nephrology, State University ofLeiden, Leiden, The Netherlands ologous IgG and IgM, respectively. Glomerular epithelial cells showed degenerative changes, but the distribution of anionic sites in the glomerular basement membrane was found to be unaltered, as determined by polyethyleneimine binding studies. In summary, an elevation of serum albumin concentration resulted in an increased transcapillary albumin transport. This was found to lead to degenerative changes of glomerular epithelial cells with development of large pore defects, which were completely reversible. (Am J Pathol 1987, 129:64-73) creased filtration ofIgG24 and ofanionic ferritin22 was found, and morphologic studies revealed detachment of glomerular epithelium from the underlying GBM,20,26 a lesion which is usually associated with a large pore defect.27-29 Immunoelectrophoresis of urinary proteins revealed that albumin constitutes the majority of filtered proteins, but a considerable proportion of the globulin fraction also reaches the urine. 13"16,19'20 In addition, the role of hemodynamic factors, such as possibly increased flows and pressures, has not been studied in detail. This article describes pathophysiologic mechanisms in protein-overload proteinuria in female Wistar rats rendered proteinuric by daily administration ofbovine serum albumin (BSA). Hematocrits, serum total protein, rat serum albumin (RSA), and BSA concentrations were monitored during and after BSA administration. Alterations in charge-and size-selective properties of the GCW after two doses of BSA were studied by measuring proteinuria and fractiona

Sdhd and Sdhd/H19 Knockout Mice Do Not Develop Paraganglioma or Pheochromocytoma

BACKGROUND: Mitochondrial succinate dehydrogenase (SDH) is a component of both the tricarboxylic acid cycle and the electron transport chain. Mutations of SDHD, the first protein of intermediary metabolism shown to be involved in tumorigenesis, lead to the human tumors paraganglioma (PGL) and pheochromocytoma (PC). SDHD is remarkable in showing an 'imprinted' tumor suppressor phenotype. Mutations of SDHD show a very high penetrance in man and we postulated that knockout of Sdhd would lead to the development of PGL/PC, probably in aged mice. METHODOLOGY/PRINCIPAL FINDINGS: We generated a conventional knockout of Sdhd in the mouse, removing the entire third exon. We also crossed this mouse with a knockout of H19, a postulated imprinted modifier gene of Sdhd tumorigenesis, to evaluate if loss of these genes together would lead to the initiation or enhancement of tumor development. Homozygous knockout of Sdhd results in embryonic lethality. No paraganglioma or other tumor development was seen in Sdhd KO mice followed for their entire lifespan, in sharp contrast to the highly penetrant phenotype in humans. Heterozygous Sdhd KO mice did not show hyperplasia of paraganglioma-related tissues such as the carotid body or of the adrenal medulla, or any genotype-related pathology, with similar body and organ weights to wildtype mice. A cohort of Sdhd/H19 KO mice developed several cases of profound cardiac hypertrophy, but showed no evidence of PGL/PC. CONCLUSIONS: Knockout of Sdhd in the mouse does not result in a disease phenotype. H19 may not be an initiator of PGL/PC tumorigenesis

Soil-wood interactions : Influence of decaying coniferous and broadleaf logs on composition of soil fungal communities

Wood-inhabiting fungi may affect soil fungal communities directly underneath decaying wood via their exploratory hyphae. In addition, differences in wood leachates between decaying tree species may influence soil fungal communities. We determined the composition of fungi in 4-yr old decaying logs of Larix kaempferi and Quercus rubra as well as in soil directly underneath and next to logs. Fungal community composition in soil covered by logs was different from that in wood and uncovered soil and was clearly influenced by the tree species. Soil fungal species richness under logs was lower than in uncovered soil but higher than in decaying wood. The amount of exploratory hyphae of log-inhabiting fungi was only high close to decaying logs. In conclusion, there is a small but significant effect of decaying coniferous and broadleaf logs on soil fungal communities directly underneath logs, likely affected by differences in wood chemistry and fungal preference between tree species

Wood Degradation by Thermotolerant and Thermophilic Fungi for Sustainable Heat Production

The use of renewable biomass for production of heat and electricity plays an important role in the circular economy. Degradation of wood biomass to produce heat is a clean and novel process proposed as an alternative to wood burning, and could be used for various heating applications. So far, wood degradation has mostly been studied at ambient temperatures. However, the process needs to occur at elevated temperatures (40-55 °C) to produce useable heat. Our objective was to study wood degradation at elevated temperatures for its potential application on heat production. Two (a thermotolerant and a thermophilic) fungi with different degradation strategies were chosen: lignin-degrading Phanerochaete chrysosporium and cellulose-degrading Chaetomium thermophilum. Each fungus was inoculated on nonsterile and sterile birch woodblocks to, respectively, study their wood degradation activity with and without natural biota (i.e., microorganisms naturally present in wood). The highest wood decay rates were found with C. thermophilum in the presence of natural biota, followed by P. chrysosporium under sterile conditions. The estimated theoretical value of heat production with C. thermophilum under nonsterile conditions was 0.6 W kg-1 wood. In conclusion, C. thermophilum seems to be a promising fungus to degrade wood together with natural biota, as sterilization of wood is not feasible in practice. Further testing on a larger scale is needed to implement the obtained results and validate the potential of biological wood degradation for heat production.</p