Fungi took a unique evolutionary route to multicellularity: Seven key challenges for fungal multicellular life

The evolution of multicellularity has been one of the major transitions in the history of life. In contrast to animals and plants, how multicellularity evolved in fungi and how it compares to the general principles distilled from the study of more widely studied model systems, has received little attention. This review broadly discusses multicellular functioning and evolution in fungi. We focus on how fungi solved some of the common challenges associated with the evolution of multi-celled organisms and what unique challenges follow from the peculiar, filamentous growth form of fungi. We identify and discuss seven key challenges for fungal multicellular growth: apical growth, compartmentalization, long-distance mass transport, controlling mutational load, cell-to-cell communication, differentiation and adhesion. Some of these are characteristic of all multicellular transitions, whereas others are unique to fungi. We hope this review will facilitate the interpretation of fungal multicellularity in comparison with that of other multicellular lineages and will prompt further research into how fungi solved fundamental challenges in one of the major transitions in their evolutionary history.     

Comparison of microbial numbers in soils by using various culture media and temperatures

The influence of different media and incubation temperatures on the quantification of microbial populations in sorghum, eucalyptus and forest soils was evaluated. Microbial growth was compared by using complex (tryptone soybean agar, TSA, casein-starch, CS, and Martin) and saline (Thorton, M3, Czapeck) media and incubation temperatures of 25 and 30 degrees C. Higher numbers of total bacterial and fungal colony-forming units (CFU) were observed in sorghum soils, and of spore-forming and Gram-negative bacteria in forest soils than other soils. Actinomycetes counts were highest in forest soil when using CS medium at 30 degrees C and in sorghum soil at 25 degrees C in M3 medium. Microorganism counts were dependent on the media and incubation temperatures. The counts at temperatures of 30 degrees C were significantly higher than at 25 degrees C. Microbial quantification was best when using TSA medium for total and spore-forming bacteria, Thorton for Gram-negative bacteria, M3 for actinomycetes, and Martin for fungi.     

Leaves as islands for microbes

Summary The equilibrium theory of island biogeography provided a framework for describing the colonization of apple leaf islands by filamentous fungi. Surface sterilization of living leaves in situ by hydrogen peroxide allowed the colonization process to be followed from its inception. Numbers of species of filamentous fungi per leaf fluctuated from 6 to 21 during the first 2 weeks of colonization and equilibrated at about 12 by the third week. Turnover occurred in species composition at equilibrium. The equilibrium number of species was not related to leaf area.The presence of an equilibrium condition with turnover on the leaf surfaces is consistent with two key tenets of the theory of island biogeography. However, the apparent back of a species-area relationship is inconsistent with the island model.     

Response of Potamogeton crispus root characteristics to sediment heterogeneity

Plant growth, biomass allocation, root distribution and plant nutrient content were investigated in the submerged macrophyte Potamogeton crispus growing in heterogeneous sediments. Three experimental sediments heterogeneous in nutrient content and phosphorus release capacity were used: sandy loam with low nutrient content (A), clay with intermediate nutrient content (B), and clay with high nutrient content (C). Biomass accumulation was significantly affected by the sediment type, and was highest in clay C (1.23 mg per plant dry weight) but lowest in sandy loam (0.69 mg per plant dry weight). The root:shoot ratios in treatments A, B and C were 0.30, 0.14 and 0.09, respectively. P. crispus allocated more biomass to roots in sandy loam compared with the other sediments. The average root numbers in sediments A, B and C were 16, 19 and 20, respectively, and the total root lengths in sediments A, B and C were 238.84, 200.36 and 187.21 cm, respectively. Almost 90% of the root biomass was distributed in the 0–15 cm depth in sediments B and C, compared with 64.53% in sediment A. The rank order of plant nitrogen and phosphorus concentrations in the sediment types was C > B > A. These results indicate that both sediment structure and nutrient availability influence the growth and distribution of the root system of P. crispus.     

Interaction between lindane and microbes in soils

Three lindane (-1,2,3,4,5,6-hexachlorocyclohexane) treated soils were studied under laboratory conditions to determine the interaction between lindane and the soil microorganisms. Microbial populations and respiration were monitored to study insecticide effects. Formation of lindane degradation products and chloride content were examined to determine effects of the microorganisms. Some populations in lindane treated soils showed temporary declines but all ultimately recovered to at least the level of the controls in 16 weeks. Respiration was stimulated over a 9-week period especially in the sandy and clay loams, suggesting the possibility of microbial degradation of the insecticide. Lindane degradation products separated and identified by TLC included -2,3,4,5,6-pentachloro-1-cyclohexene (-PCCH), -3,4,5,6-tetrachloro-1-cyclohexene (-TCCH), -3,4,5,6-tetrachloro-1-cyclohexene (-TCCH), and pentachlorobenzene (PCB). Chloride production increased in soils treated with higher levels of lindane.Contribution No. 609, Research Institute, Agriculture Canada, University Sub Post Office, London, Ontario N6A 5B7.     

Industrial mycology and the new genetics

Summary The genetic investigation of fungi has been extended substantially by DNA-mediated transformation, providing a supplement to more conventional genetic approaches based upon sexual and parasexual processes. Initial transformation studies with the yeastSaccharomyces cerevisiae provided the model for transformation systems in other fungi with regard to methodology, vector construction and selection strategies. There are, however, certain differences betweenS. cerevisiae and filamentous fungi with regard to type of genomic insertion and the availability of shuttle vectors. Single-site linked insertions are common in yeast due to the high level of homology required for recombination between vectored and genomic sequences, whereas mycelial fungi often show a high frequency of heterologous and unlinked insertions, often in the form of random and multiple-site integrations. While extrachromosomally-maintained or replicative vectors are readily available for use with yeasts, such vectors have been difficult to construct for use with filamentous fungi. The development of vectors for replicative transformation with these fungi awaits further study. It is proposed that replicative vectors may be inherently less efficient for use with mycelial fungi relative to yeasts, since the mycelium, as an extended and semicontinuous network of cells, may delimit an adequate diffusion of the vector carrying the selectable gene, thus leading to a high frequency of abortive or unstable transformants.Based on the Charles Thom Award Lecture presented to the Society for Industrial Microbiology on August 4, 1994.     

Effect of soil fumigation with vapam on the dynamics of soil microflora and their related biochemical activity

Summary Fungal propagules, in general, were drastically reduced in vapam amended soils. The toxicant from 250 to 1000 ppm was lethal toFusarium spp. Only in the early part of the experiment, higher concentrations of vapam appreciably reduced the population of bacteria and actinomycetes, though later on, their population gradually increased. The numbers of Azotobacter in soil amended with 125, 250 and 500 ppm did not alter appreciably, but their population in treated soils increased over the check on the 45th day. All concentrations of vapam lowered the population of Rhizobia.Vapam produced inhibitory effect on soil nitrification, inhibition period varying with the amount of chemical applied initially. Vapam from 125 to 500 ppm stimulated the ammonification process, while its higher concentration (1000 ppm) produced detrimental effect for 15 days. The toxicant increased CO₂ production for first 32 days.Results suggest that extraordinary success of vapam in controlling soil-borne infections of Pythium and Rhizoctonia was not entirely due to its fungicidal action. Partly it was also due to an increase in the population of known antagonists of these pathogens in fumigated soils.     

The effect of heterogeneity on optimal regimens in cancer chemotherapy

Optimal drug regimens for cancer chemotherapy are determined when knowledge is only available on the behaviour of the tumour and the drugs used, over a population of patients. The case of two drugs is investigated where they are equivalent on average. Our calculations indicate that the optimal regimen has both drugs given initially but then sequences the two drugs. Our calculations also indicate that as tumour heterogeneity increases, the benefit to be gained from the optimal regimen can decrease in comparison to reasonable regimens. This has the effect of complicating the calculation of optimal regimens in a clinical setting, and may explain why results in experimental oncology fail to carry over to clinical oncology.     

Prevalence and distribution of airborne and waterborne fungi and actinomycetes in the Nile river

The objective of this research was to investigate the prevalence and distribution of airborne and waterborne fungi and actinomycetes along the main stream of the Nile river during April to July, 2005. Air and water samples were collected at eight sites within a ~50 km stretch of the river. The distribution and prevalence of air and water microorganisms varied with location. The highest counts of airborne fungi (516 CFU/p/h) and actinomycetes (222 CFU/p/h) were detected at suburban sites near cultivated areas. However, the highest counts of waterborne fungi (56.4 CFU/ml) and actinomycetes (15.4 CFU/ml) were detected at Al-Galaa (city centre) and Kafr-El-elwe (south Cairo), respectively. A total of 1,816 fungal colonies (943 isolates from air and 873 from water samples) belonging to 27 genera were identified. Aspergillus, Alternaria, Cladosporium, and yeasts were the predominant fungal types in both air and water environments. Dreschlera, Emericella, Nigrospora, Spicaria, Stachybotrys, and Verticillium were only detected in the air, and Epicoccum, Philaphora, Phoma and Ulocladium were only detected in the water. Mycotoxin-producing fungi represented by Aspergillus flavus, Aspergillus parasiticus, Penicillium, Fusarium, and Trichoderma were found in the air and water environments. Significant differences (P ≤ 0.05) were found between fungal populations in air and water at different sampling sites. No significant differences (P ≥ 0.05) were found between waterborne actinomycetes. Sampling location, human activity, and pollution load are the main factors affecting the variability and biodiversity of microorganisms in different microenvironments.     

Microbial populations in trifluralin-treated soil

Summary This study examined the effects of trifluralin (,,-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), a soil incorporated herbicide, on soil microflora both in the general soil environment and in the rhizosphere of trifluralin damaged wheat roots. Two Dark Brown Chernozemic soils were treated with various trifluralin rates in the growth chamber and wheat [Triticum aestivum L. Neepawa] was seeded. Trifluralin generally had no effect on fungi, bacteria, or actinomycete populations in either the general soil or in the rhizosphere. CO₂ evolution was unchanged when trifluralin was added to the soil. In wheat plots, at two field locations, there were no significant effects of trifluralin (1.0 kg ha^–1) on soil fungi, bacteria, actinomycete, denitrifying bacteria, and nitrifying Nitrobacter propulations. A pure culture study with 42 soil microorganisms showed that many isolates were inhibited at 400 to 100,000 g g^–1 but not at concentrations <16 g g^–1. Similar data were obtained from tests on four different soils. These studies indicate that trifluralin is unlikely to cause changes in the numbers of soil microorganisms when used at recommended levels.     

Single cell heterogeneity in human pluripotent stem cells

Human pluripotent stem cells (hPSCs) include human embryonic stem cells (hESCs) derived from blastocysts and human induced pluripotent stem cells (hiPSCs) generated from somatic cell reprogramming. Due to their self-renewal ability and pluripotent differentiation potential, hPSCs serve as an excellent experimental platform for human development, disease modeling, drug screening, and cell therapy. Traditionally, hPSCs were considered to form a homogenous population. However, recent advances in single cell technologies revealed a high degree of variability between individual cells within a hPSC population. Different types of heterogeneity can arise by genetic and epigenetic abnormalities associated with long-term in vitro culture and somatic cell reprogramming. These variations initially appear in a rare population of cells. However, some cancer-related variations can confer growth advantages to the affected cells and alter cellular phenotypes, which raises significant concerns in hPSC applications. In contrast, other types of heterogeneity are related to intrinsic features of hPSCs such as asynchronous cell cycle and spatial asymmetry in cell adhesion. A growing body of evidence suggests that hPSCs exploit the intrinsic heterogeneity to produce multiple lineages during differentiation. This idea offers a new concept of pluripotency with single cell heterogeneity as an integral element. Collectively, single cell heterogeneity is Janus-faced in hPSC function and application. Harmful heterogeneity has to be minimized by improving culture conditions and screening methods. However, other heterogeneity that is integral for pluripotency can be utilized to control hPSC proliferation and differentiation.     

Growth responses of some soil fungi to spatially heterogeneous nutrients

Abstract The natural nutritional environments of most fungi are spatially non-uniform, yet the majority of studies of fungal growth take no account of this fact. An experimental system is described which permits the growth responses of eucarpic fungi to heterogeneously distributed nutrient resources to be studied. The system comprises tesselations of agar tiles of contrasting nutrient status separated by air gaps. Growth responses in such systems of Alternaria alternata, Mucor sp., Phoma foveata , Rhizoctonia solani and Trichoderma viride are described. Generally, the growth of the fungi reflected the nutrient status of the underlying substrate. There was evidence for growth in low-nutrient tiles being greater when high-nutrient tiles were included in the tessellation. Reproductive structures tended to be formed only in low nutrient tiles with Trichoderma and Rhizoctonia and only high nutrient tiles with Alternaria . Growth responses of Rhizoctonia were strongly asymmetric in nutritionally symmetric, but heterogeneous, tesselations. The consequences of the observations for fungal growth in heterogeneous environments such as soil is discussed.     

Quantifying the branching frequency of virtual filamentous microbes using fractal analysis

The productivity of an industrial fermentation process involving a filamentous microbe is heavily dependent on the morphological form adopted by the organism. The development of systems capable of rapidly and accurately characterizing morphology within a given process represents a significant challenge, as the complex phenotypes that are manifested are not easily quantified. Conventional parameters employed in these analyses are often of limited value, as they reveal little about the branching behavior of the organism; an important consideration given the demonstrated link between branching frequency and metabolite production. In this study, the influence of branching behavior on the spatial distribution of mycelia grown in silico is examined through fractal analysis. It is demonstrated that fractal dimension, quantified based on the frequency distribution of parameterized boundary curves, and lacunarity act as robust estimators of branching behavior. The analysis can, in theory, be applied to any morphological form, providing universally applicable process parameters for more complete data acquisition. Biotechnol. Bioeng. 2013; 110: 437–447. © 2012 Wiley Periodicals, Inc.     

Airborne dust,bacteria, actinomycetes and fungi at a flourmill

A study was carried out on suspended dust, bacterial and fungal aerosols in a four-storey flourmill building located in Giza, Egypt. Airborne microorganisms were quantitatively isolated using liquid impinger and gravimetric samplers during the period from March 2004 to February 2005. Suspended dust varied from 1.96 to 16.3 mg m⁻³ and 0.69 to 1.8 mg m⁻³ in the indoor and outdoor environments, respectively. Suspended dust was significantly greater (P < 0.05) at bran package, double roller, purifiers and flour storage units in comparison to the outdoor reference site. The dust levels exceed the occupational exposure limit (OEL) of 0.5 mg m⁻³ for flour dust. Airborne microbial counts were found at median values, between sampling locations, ranged from 0 to >10⁴ CFU m⁻³. Gram-negative bacteria were found in small numbers (0–10² CFU m⁻³). The highest concentration of actinomycetes (>10³ CFU m⁻³) was detected in the storage unit. Airborne fungal counts were found at the median values, between sampling locations, varied from 10³ to 10⁴ CFU m⁻³. The counts of airborne bacteria and fungi were significantly greater (P < 0.05) at the purifiers and double roller mill units in comparison to the outdoor reference site using the liquid impinger sampler. Microbial levels associated with bulk deposited dust averaged between 10⁵ and 10⁶ CFU g⁻¹. Alcaligenes (5.4%) Pseudomonas (3.87%) and Enterobacter (3.1%) were the predominant Gram-negative species while Bacillus (29.4%) and Micrococci (13.9%) were the major components of Gram-positive bacteria. Aspergillus and Penicillium were the predominant fungal types indoor whereas Cladosporium (35.2%) and Aspergillus species (22.2%) were the predominant fungal types outdoor. A number of allergenic and toxigenic bioaerosols were found in the flourmill workplace.     

Molecular heterogeneity of tumor endothelium

Tumors depend on a vascular supply for their growth. Tumor blood vessels, which are derived from normal tissue vasculature, display a markedly abnormal phenotype. Tumor endothelial properties are highly varied in space and time. An important goal is to delineate the range of phenotypes in tumor endothelium and to identify tumor endothelial-specific molecular signatures. This information should lead to a more complete understanding of the mechanisms of tumor growth, the discovery of new therapeutic targets, and the development of biomarkers for diagnosis and surveillance. The goals of this review are to outline recent advances in dissecting tumor endothelial-cell-specific gene expression, to address mechanisms of phenotypic heterogeneity in tumor vascular beds, and to discuss the therapeutic implications of these findings.     

Accommodating unmodeled heterogeneity in double-observer distance sampling surveys

Mark-recapture models applied to double-observer distance sampling data neglect the information on relative detectability of objects contained in the distribution of observed distances. A difference between the observed distribution and that predicted by the mark-recapture model is symptomatic of a failure of the assumption of zero correlation between detection probabilities implicit in the mark-recapture model. We develop a mark-recapture-based model that uses the observed distribution to relax this assumption to zero correlation at only one distance. We demonstrate its usefulness in coping with unmodeled heterogeneity using data from an aerial survey of crabeater seals in the Antarctic.     

Myco-chitinases as versatile biocatalysts for translation of coastal residual resources to eco-competent chito-bioactives

Chitinases (EC 3.2.1.14) are the glycoside hydrolases (GH) that catalyse the cleavage of β-(1,4) glycosidic linkages of chitin, which is a key element of fungal cell wall and insect's exoskeletons. Fungi have been considered as an excellent source for the production of extracellular chitinases, which could further be employed for chitin degradation to generate a range of bioactive chito-derivatives, i.e., oligosaccharides and glucosamine. Moreover, chitinases have diverse roles in various physiological functions, i.e., autolysis, cell wall remodeling, mycoparasitism and biocontrol. The advent of technology led to the sequencing of several fungal genomes and enabled the manipulation of novel effective chitinase genes to investigate their mechanistic and structural insights to decode the variabilities in chitin degradation. Further, the comprehensible understanding of attributes including substrate-binding sites and catalytic domains could give an insight into chitin catabolism for value-added products development. The review summarized various aspects of fungal chitinases viz. structure, mechanism, classification, properties, functions and application in the present precis. The study has also underlined the recent research related to the framework of substrate-binding clefts in fungal chitinases and its correlation with the hydrolytic and transglycosylation (TG) activity for the production of oligosaccharides with variable degrees of polymerization.     

Effects of Cultivation Parameters on the Morphology of Rhizopus arrhizus and the Lactic Acid Production in a Bubble Column Reactor

The use of filamentous Rhizopus for lactic acid production is facing a challenge due to its low yield mainly caused by the difficulty to control its morphology in submerged fermentation processes. This study was aimed at investigating the impacts of cultivation parameters on the morphology of Rhizopus arrhizus DAR 36017 and lactic acid production using waste potato starch in a laboratory scale bubble column reactor (BCR). The fungal morphology was significantly influenced by carbon sources, process pH, starch concentrations, sparger designs and aeration rates. The favorable morphology for lactic acid production was a freely dispersed small pellet, which was achieved under operation conditions at pH 5.0–6.0, starch concentrations of 60–120 g/L and aeration rates of 0.2–0.8 vvm using a sintered stainless steel disc sparger. Optimal cultivation conditions at pH 6.0 and an aeration rate of 0.4 vvm resulted in the formation of freely dispersed small pellets and 103.8 g/L lactic acid with a yield of 87 % from 120 g/L liquefied potato starch in 48 h. The overall results in terms of lactic acid yield and productivity are comparable to those reported in previous studies using immobilized Rhizopus cells in batch fermentations.     

Epithelial cell plasticity defines heterogeneity in lung cancer

Lung cancer is the leading cause of cancer death for both men and women and accounts for almost 18.4% of all deaths due to cancer worldwide, with the global incidence increasing by approximately 0.5% per year. Lung cancer is regarded as a devastating type of cancer owing to its high prevalence, reduction in the health-related quality of life, frequently delayed diagnosis, low response rate, high toxicity, and resistance to available therapeutic options. The highly heterogeneous nature of this cancer with a proximal-to-distal distribution throughout the respiratory tract dramatically affects its diagnostic and therapeutic management. The diverse composition and plasticity of lung epithelial cells across the respiratory tract are regarded as significant factors underlying lung cancer heterogeneity. Therefore, definitions of the cells of origin for different types of lung cancer are urgently needed to understand lung cancer biology and to achieve early diagnosis and develop cell-targeted therapies. In the present review, we will discuss the current understanding of the cellular and molecular alterations in distinct lung epithelial cells that result in each type of lung cancer.     

Capillary electrophoresis for the investigation of prostate-specific antigen heterogeneity

Prostate-specific antigen (PSA) is a single-chain glycoprotein that is used as a biomarker for prostate-related diseases. PSA has one known posttranslational modification, a sialylated diantennary N-linked oligosaccharide attached to the asparagine residue N45. In this study capillary electrophoresis (CE) was employed to separate the isoforms of seven commercially available free PSA samples, two of which were specialized: enzymatically active PSA and noncomplexing PSA. The free PSA samples examined migrated as four to nine distinct, highly resolved peaks, indicating the presence of several isoforms differing in their oligosaccharide compositions. Overall, the use of CE provides a rapid, reproducible method for separation of PSA into its individual isoforms.