scholarly journals STUDIES ON A CYTOPLASMIC CHARACTER IN NEUROSPORA CRASSA

1965 ◽  
Vol 26 (2) ◽  
pp. 413-425 ◽  
Author(s):  
Laura Garnjobst ◽  
J.F. Wilson ◽  
E. L. Tatum
Keyword(s):  
Growth Rate ◽  
Oxygen Consumption ◽  
Neurospora Crassa ◽  
Great Variability ◽  
Wild Type ◽  
Aerial Hyphae ◽  
Genetic Strains ◽  
First Time ◽  
Slow Growing ◽  
Microinjection Techniques

Two morphologically distinctive slow growing strains of Neurospora crassa have been isolated and studied. These, abn-1 and abn-2, differ from wild type in that their growth rates are greatly reduced and often irregular, aerial hyphae are absent, conidia are extremely rare, and no protoperithecia are formed. Growth was not improved by addition of any nutrients tested, oxygen consumption was similar to that of wild type, and cytochrome c appeared abnormally high, and b low or absent. Both abn strains gave rise only to normal progeny in crosses with normal strains. The abn characteristics appear in heterocaryons, and have been transmitted to other genetic strains by means of heterocaryosis followed by plating of conidia. Conidia formed by such heterocaryons typically showed low viability, and gave rise to cultures with great variability in growth rate, morphology, and survival. Even apparently normal derived cultures often later became abnormal or died. It is concluded that the abnormal characteristics are determined primarily by cytoplasmic factors. This conclusion was strengthened by the transmission of the typical characteristics to normal strains by microinjection of cytoplasm from abn cultures, even without demonstrable transfer of nuclei. This constitutes the first time microinjection techniques have been successfully applied to the analysis of a cytoplasmic character in Neurospora.

scholarly journals Mutational Activation of a Gαi Causes Uncontrolled Proliferation of Aerial Hyphae and Increased Sensitivity to Heat and Oxidative Stress in Neurospora crassa

Genetics ◽  
1999 ◽  
Vol 151 (1) ◽  
pp. 107-117
Author(s):  
Qi Yang ◽  
Katherine A Borkovich
Keyword(s):  
Signal Transduction ◽  
Neurospora Crassa ◽  
Signal Transduction Pathway ◽  
Sexual Cycle ◽  
Intracellular Camp ◽  
Wild Type ◽  
Independent Functions ◽  
Aerial Hyphae ◽  
Mutational Activation ◽  
Camp Levels

Abstract Heterotrimeric G proteins, consisting of α, β, and γ subunits, transduce environmental signals through coupling to plasma membrane-localized receptors. We previously reported that the filamentous fungus Neurospora crassa possesses a Gα protein, GNA-1, that is a member of the Gαi superfamily. Deletion of gna-1 leads to defects in apical extension, differentiation of asexual spores, sensitivity to hyperosmotic media, and female fertility. In addition, Δgna-1 strains have lower intracellular cAMP levels under conditions that promote morphological abnormalities. To further define the function of GNA-1 in signal transduction in N. crassa, we examined properties of strains with mutationally activated gna-1 alleles (R178C or Q204L) as the only source of GNA-1 protein. These mutations are predicted to inhibit the GTPase activity of GNA-1 and lead to constitutive signaling. In the sexual cycle, gna-1R178C and gna-1Q204L strains are female-fertile, but produce fewer and larger perithecia than wild type. During asexual development, gna-1R178C and gna-1Q204L strains elaborate abundant, long aerial hyphae, produce less conidia, and possess lower levels of carotenoid pigments in comparison to wild-type controls. Furthermore, gna-1R178C and gna-1Q204L strains are more sensitive to heat shock and exposure to hydrogen peroxide than wild-type strains, while Δgna-1 mutants are more resistant. In contrast to Δgna-1 mutants, gna-1R178C and gna-1Q204L strains have higher steady-state levels of cAMP than wild type. The results suggest that GNA-1 possesses several Gβγ-independent functions in N. crassa. We propose that GNA-1 mediates signal transduction pathway(s) that regulate aerial hyphae development and sensitivity to heat and oxidative stresses, possibly through modulation of cAMP levels.

scholarly journals The ham-2 Locus, Encoding a Putative Transmembrane Protein, Is Required for Hyphal Fusion in Neurospora crassa

Genetics ◽  
2002 ◽  
Vol 160 (1) ◽  
pp. 169-180
Author(s):  
Qijun Xiang ◽  
Carolyn Rasmussen ◽  
N Louise Glass
Keyword(s):  
Neurospora Crassa ◽  
Somatic Cell ◽  
Molecular Mechanism ◽  
Cell Fusion ◽  
Deletion Mutant ◽  
Transmembrane Protein ◽  
Wild Type ◽  
Vegetative Incompatibility ◽  
Hyphal Fusion ◽  
Aerial Hyphae

Abstract Somatic cell fusion is common during organogenesis in multicellular eukaryotes, although the molecular mechanism of cell fusion is poorly understood. In filamentous fungi, somatic cell fusion occurs during vegetative growth. Filamentous fungi grow as multinucleate hyphal tubes that undergo frequent hyphal fusion (anastomosis) during colony expansion, resulting in the formation of a hyphal network. The molecular mechanism of the hyphal fusion process and the role of networked hyphae in the growth and development of these organisms are unexplored questions. We use the filamentous fungus Neurospora crassa as a model to study the molecular mechanism of hyphal fusion. In this study, we identified a deletion mutant that was restricted in its ability to undergo both self-hyphal fusion and fusion with a different individual to form a heterokaryon. This deletion mutant displayed pleiotropic defects, including shortened aerial hyphae, altered conidiation pattern, female sterility, slow growth rate, lack of hyphal fusion, and suppression of vegetative incompatibility. Complementation with a single open reading frame (ORF) within the deletion region in this mutant restored near wild-type growth rates, female fertility, aerial hyphae formation, and hyphal fusion, but not vegetative incompatibility and wild-type conidiation pattern. This ORF, which we named ham-2 (for hyphal anastomosis), encodes a putative transmembrane protein that is highly conserved, but of unknown function among eukaryotes.

scholarly journals Characterization of Neurospora crassa cyclic AMP phosphodiesterase activated by calmodulin

1985 ◽  
Vol 232 (2) ◽  
pp. 425-430 ◽  
Author(s):  
M T Téllez-Iñón ◽  
R M Ulloa ◽  
G C Glikin ◽  
H N Torres
Keyword(s):  
Cyclic Amp ◽  
Neurospora Crassa ◽  
Cyclic Nucleotide ◽  
Neuroleptic Drugs ◽  
Wild Type ◽  
Cyclic Amp Phosphodiesterase ◽  
Aerial Hyphae

Activation of cyclic AMP phosphodiesterase I by brain or Neurospora calmodulin was studied. The stimulation required micromolar concentrations of Ca2+, and it was observed at cyclic AMP concentrations between 0.1 and 500 microM. Activation was blocked by EDTA and some neuroleptic drugs such as chlorpromazine and fluphenazine. These drugs inhibit the elongation of N. crassa wild-type aerial hyphae. These results reinforce the evidence towards the recognition of Ca2+-calmodulin as one of the systems controlling cyclic nucleotide concentrations in Neurospora.

scholarly journals Ferredoxin-NADP+ Reductase from Pseudomonas putida Functions as a Ferric Reductase

2008 ◽  
Vol 191 (5) ◽  
pp. 1472-1479 ◽  
Author(s):  
Jinki Yeom ◽  
Che Ok Jeon ◽  
Eugene L. Madsen ◽  
Woojun Park
Keyword(s):  
Growth Rate ◽  
Pseudomonas Putida ◽  
Reductase Activity ◽  
Flavin Mononucleotide ◽  
Flavin Reductase ◽  
Ferric Reductase ◽  
Wild Type ◽  
Cell Extracts ◽  
Mutant Strains ◽  
First Time

ABSTRACT Pseudomonas putida harbors two ferredoxin-NADP+ reductases (Fprs) on its chromosome, and their functions remain largely unknown. Ferric reductase is structurally contained within the Fpr superfamily. Interestingly, ferric reductase is not annotated on the chromosome of P. putida. In an effort to elucidate the function of the Fpr as a ferric reductase, we used a variety of biochemical and physiological methods using the wild-type and mutant strains. In both the ferric reductase and flavin reductase assays, FprA and FprB preferentially used NADPH and NADH as electron donors, respectively. Two Fprs prefer a native ferric chelator to a synthetic ferric chelator and utilize free flavin mononucleotide (FMN) as an electron carrier. FprB has a higher k cat/Km value for reducing the ferric complex with free FMN. The growth rate of the fprB mutant was reduced more profoundly than that of the fprA mutant, the growth rate of which is also lower than the wild type in ferric iron-containing minimal media. Flavin reductase activity was diminished completely when the cell extracts of the fprB mutant plus NADH were utilized, but not the fprA mutant with NADPH. This indicates that other NADPH-dependent flavin reductases may exist. Interestingly, the structure of the NAD(P) region of FprB, but not of FprA, resembled the ferric reductase (Fre) of Escherichia coli in the homology modeling. This study demonstrates, for the first time, the functions of Fprs in P. putida as flavin and ferric reductases. Furthermore, our results indicated that FprB may perform a crucial role as a NADH-dependent ferric/flavin reductase under iron stress conditions.

Production of tumours and roots by Ephedra following Agrobacterium rhizogenes infection

1994 ◽  
Vol 72 (2) ◽  
pp. 203-207 ◽  
Author(s):  
Niamh A. O'Dowd ◽  
David H. S. Richardson
Keyword(s):  
Growth Rate ◽  
Plant Growth ◽  
Agrobacterium Rhizogenes ◽  
Dry Weight ◽  
Wild Type ◽  
Bacterial Strains ◽  
Heat Treated ◽  
Slow Growing

This paper contains the first report that stems of the Gnetophyte Ephedra respond to infection by Agrobacterium rhizogenes by producing roots and tumours in vivo and in vitro. Of the bacterial strains employed, the wild-type Ar2629 gave the maximum response, and strain LBA9402 was also effective. In no case did heat-treated A. rhizogenes produce tumours or roots. Excised tumour tissues were cultured for more than 2 years in the absence of exogenous plant-growth regulators without any deterioration in growth rate. In vivo tumours of Ephedra fragilis and Ephedra minima contained up to 0.3% dry weight l-ephedrine, and slow-growing in vitro cultured tumours of E. fragilis contained up to 0.01% l-ephedrine, but alkaloid was not detected in faster growing isolates. Key words: Agrobacterium rhizogenes, alkaloid, Ephedra, l-ephedrine, Gnetophytes, gymnosperm, tumours.

scholarly journals Shared and Independent Roles for a Gαi Protein and Adenylyl Cyclase in Regulating Development and Stress Responses in Neurospora crassa

2002 ◽  
Vol 1 (4) ◽  
pp. 634-642 ◽  
Author(s):  
F. Douglas Ivey ◽  
Ann M. Kays ◽  
Katherine A. Borkovich
Keyword(s):  
Neurospora Crassa ◽  
Adenylyl Cyclase ◽  
Stress Responses ◽  
Growth And Development ◽  
Submerged Culture ◽  
Wild Type Strain ◽  
Wild Type ◽  
Liquid Cultures ◽  
Aerial Hyphae ◽  
Gαi Protein

ABSTRACT Growth and development are regulated using cyclic AMP (cAMP)-dependent and -independent pathways in Neurospora crassa. The cr-1 adenylyl cyclase mutant lacks detectable cAMP and exhibits numerous defects, including colonial growth habit, short aerial hyphae, premature conidiation on plates, inappropriate conidiation in submerged culture, and increased thermotolerance. Evidence suggests that the heterotrimeric Gα protein GNA-1 is a direct positive regulator of adenylyl cyclase. Δgna-1 strains are female-sterile, and Δgna-1 strains have reduced apical extension rates on normal and hyperosmotic medium, greater resistance to oxidative and heat stress, and stunted aerial hyphae compared to the wild-type strain. In this study, a Δgna-1 cr-1 double mutant was analyzed to differentiate cAMP-dependent and -independent signaling pathways regulated by GNA-1. Δgna-1 cr-1 mutants have severely restricted colonial growth and do not produce aerial hyphae on plates or in standing liquid cultures. Addition of cAMP to plates or standing liquid cultures rescues cr-1, but not Δgna-1 cr-1, defects, which is consistent with previous results demonstrating that Δgna-1 mutants do not respond to exogenous cAMP. The females of all strains carrying the Δgna-1 mutation are sterile; however, unlike cr-1 and Δgna-1 strains, the Δgna-1 cr-1 mutant does not produce protoperithecia. The Δgna-1 and cr-1 mutations were synergistic with respect to inappropriate conidiation during growth in submerged culture. Thermotolerance followed the order wild type < Δgna-1 < cr-1 = Δgna-1 cr-1, consistent with a cAMP-dependent process. Taken together, the results suggest that in general, GNA-1 and CR-1 regulate N. crassa growth and development using parallel pathways, while thermotolerance is largely dependent on cAMP.

scholarly journals The Endospore-Forming Pathogen Bacillus cereus Exploits a Small Colony Variant-Based Diversification Strategy in Response to Aminoglycoside Exposure

mBio ◽  
2015 ◽  
Vol 6 (6) ◽  
Author(s):  
Elrike Frenzel ◽  
Markus Kranzler ◽  
Timo D. Stark ◽  
Thomas Hofmann ◽  
Monika Ehling-Schulz
Keyword(s):  
Antibiotic Resistance ◽  
Bacillus Cereus ◽  
Differential Diagnostics ◽  
Wild Type ◽  
Content Type ◽  
Small Colony Variant ◽  
Enhanced Production ◽  
Small Colony ◽  
First Time ◽  
Slow Growing

ABSTRACTBacillus cereusis among the microorganisms most often isolated from cases of food spoilage and causes gastrointestinal diseases as well as nongastrointestinal infections elicited by the emetic toxin cereulide, enterotoxins, and a panel of tissue-destructive virulence factors. This opportunistic pathogen is increasingly associated with rapidly fatal clinical infections especially linked to neonates and immunocompromised individuals. Fatality results from either the misdiagnosis ofB. cereusas a contaminant of the clinical specimen or from failure of antibiotic therapy. Here we report for the first time that exposure to aminoglycoside antibiotics induces a phenotype switching of emeticB. cereussubpopulations to a slow-growing small colony variant (SCV) state. Along with altered antibiotic resistance, SCVs showed distinct phenotypic and metabolic properties, bearing the risk of antibiotic treatment failure and of clinical misdiagnosis by standard identification tests used in routine diagnostic. The SCV subpopulation is characterized by enhanced production of the toxin cereulide, but it does not secrete tissue-destructive and immune system-affecting enzymes such as sphingomyelinase and phospholipase. SCVs showed significantly prolonged persistence and decreased virulence in theGalleria mellonellamodel for bacterial infections, indicating diversification concerning their ecological lifestyle. Importantly, diversification into coexisting wild-type and SCV subpopulations also emerged during amikacin pressure duringin vivoinfection experiments.IMPORTANCEThis study shows for the first time that pathogenic spore-formingB. cereusstrains are able to switch to a so far unreported slow-growing lifestyle, which differs substantially in terms of developmental, phenotypic, metabolic, and virulence traits from the wild-type populations. This underpins the necessity of molecular-based differential diagnostics and a well-chosen therapeutic treatment strategy in clinical environments to combatB. cereusin a tailored manner. The reported induction of SCV in an endospore-forming human pathogen requires further research to broaden our understanding of a yet unexplored antibiotic resistance mechanism in sporulating bacteria. Our work also raises a general question about the ecological meaning of SCV subpopulation emergence and importance of SCV in sporeformer populations as an alternative route, next to sporulation, to cope with stresses encountered in natural niches, such as soil or host interfaces.

scholarly journals Estimating the growth rate in desert biological rock crusts by integrating archaeological and geological records

2021 ◽  
Author(s):  
Nimrod Wieler ◽  
Tali Erickson Gini ◽  
Osnat Gillor ◽  
Roey Angel
Keyword(s):  
Growth Rate ◽  
Archaeological Site ◽  
Arid Environment ◽  
Building Stone ◽  
Archaeological Sites ◽  
Arid Environments ◽  
Natural Conditions ◽  
Stone Block ◽  
First Time ◽  
Slow Growing

Abstract. Biological rock crusts (BRCs) are ubiquitous features of rock surfaces in drylands composed of slow-growing microbial assemblages. BRC presence is often correlated with rock weathering, soiling effect, or with mitigating geomorphic processes. However, their development rate has not been quantified. In this work, we characterised and dated BRCs in an arid environment, under natural conditions, by integrating archaeological, microbiological and geological methods. To this end, we sampled rocks from a well-documented Byzantine archaeological site, and the surrounding area located in the Central Negev Desert, Israel. The archaeological, which is dated to the 4th–7th centuries CE, was constructed from two lithologies, limestone and chalk. BRC started developing on the rocks after being carved, and its age should match that of the site. The BRC samples showed mild differences in the microbial community assemblages between the site and its surrounding, irrespective of lithology, and were dominated by Actinobacteria, Cyanobacteria and Proteobacteria. We further measured the BRC thickness, valued at 0.1–0.6 mm thick BRC on the surface of 1700 years old building stone block of about 0.1 square metres. Therefore, a BRC growth rate was estimated, for the first time, to be 0.06–0.35 mm 1000 yr−1. We propose that BRC growth rates could be used as an affordable yet robust dating tool in archaeological sites in arid environments.

scholarly journals Tests of a Cellular Model for Constant Branch Distribution in the Filamentous Fungus Neurospora crassa

2001 ◽  
Vol 67 (4) ◽  
pp. 1788-1792 ◽  
Author(s):  
Michael K. Watters ◽  
Anthony J. F. Griffiths
Keyword(s):  
Growth Rate ◽  
Neurospora Crassa ◽  
Tip Growth ◽  
Extension Rate ◽  
Mycelial Fungi ◽  
Organic Substrates ◽  
Cellular Model ◽  
Wild Type ◽  
Tip Extension ◽  
Pass Through

ABSTRACT The growth of mycelial fungi is characterized by the highly polarized extension of hyphal tips and the formation of subapical branches, which themselves extend as new tips. In Neurospora crassa, tip growth and branching are crucial elements for this saprophyte in the colonization and utilization of organic substrates. Much research has focused on the mechanism of tip extension, but a cellular model that fully explains the known phenomenology of branching by N. crassa has not been proposed. We described and tested a model in which the formation of a lateral branch in N. crassa was determined by the accumulation of tip-growth vesicles caused by the excess of the rate of supply over the rate of deposition at the apex. If both rates are proportional to metabolic rate, then the model explains the known lack of dependence of branch interval on growth rate. We tested the model by manipulating the tip extension rate, first by shifting temperature in both the wild type and hyperbranching (colonial) mutants and also by observing the behavior of both tipless colonies and colonyless tips. We found that temperature shifts in either direction result in temporary changes in branching. We found that colonyless tips also pass through a temporary transition phase of branching. The tipless colonies produced a cluster of new tips near the point of damage. We also found that branching in colonial mutants is dependent on growth rate. The results of these tests are consistent with a model of branching in which branch initiation is controlled by the dynamics of tip growth while being independent of the actual rate of this growth.

Ultrastructure and Morphology of the Neurospora Crassa Cell Wall Mutants, Slime And Slime X, Using Tem and Sem

1976 ◽  
Vol 34 ◽  
pp. 54-55
Author(s):  
Karen S. Howard ◽  
H. D. Braymer ◽  
M. D. Socolofsky ◽  
S. A. Milligan
Keyword(s):  
Cell Wall ◽  
Neurospora Crassa ◽  
Wild Type ◽  
Morphological Comparison ◽  
Small Areas ◽  
Solid Media ◽  
Thin Sectioning ◽  
X Cells ◽  
Mutant Cells ◽  
Isolated Cell

The recently isolated cell wall mutant slime X of Neurospora crassa was prepared for ultrastructural and morphological comparison with the cell wall mutant slime. The purpose of this article is to discuss the methods of preparation for TEM and SEM observations, as well as to make a preliminary comparison of the two mutants.TEM: Cells of the slime mutant were prepared for thin sectioning by the method of Bigger, et al. Slime X cells were prepared in the same manner with the following two exceptions: the cells were embedded in 3% agar prior to fixation and the buffered solutions contained 5% sucrose throughout the procedure.SEM: Two methods were used to prepare mutant and wild type Neurospora for the SEM. First, single colonies of mutant cells and small areas of wild type hyphae were cut from solid media and fixed with OSO4 vapors similar to the procedure used by Harris, et al. with one alteration. The cell-containing agar blocks were dehydrated by immersion in 2,2-dimethoxypropane (DMP).

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