Publisher Summary This chapter discusses the cell wall synthesis in apical hyphal growth. It appears that the hyphal apex is best viewed as a highly polarized system of exocytosis. Wall materials, extracellular enzymes, and probably other substances are excreted at the growing end of a tubular cell. The most obvious cellular features that accompany this polarized system are (1) the unidirectional flow of vesicles in the cytoplasm fusing with the plasma membrane at the apex, (2) the gradients in wall synthesis at the apex, and (3) the cytoplasmic gradients in ion distribution that are maintained at the apex. New microscopic techniques reveal a cytoskeletal organization of the cytoplasm at the apex, which may be crucial to its polarized activity. Growth of the wall at the hyphal apex requires that the wall in this region has plastic properties, which contrast with the requirement of rigidity elsewhere in the hypha. A widely held view involves the participation of wall-lytic enzymes in plasticizing the wall at the apex and in allowing new wall material to be inserted. A critical evaluation of the evidence presented to support this view makes this hypothesis less attractive. As an alternative a steady-state model is discussed based on recent observations in the author's laboratory. This model holds that the assemblage of polymers synthesized at the apex is inherently plastic. However, this assemblage develops rigidity by interactions, in the wall, between and among the various individual polymers present while the wall segment moves in subapical directions during elongation. This model seems to fit many of the original observations made on living hyphae.

Cell-wall synthesis in apical hyphal growth

Foreword J. Seckbach Introduction N. Gunde-Cimerman, A. Oren, A. Plemenitas SECTION I. THE ENVIRONMENTS AND THEIR DIVERSITY Microbial diversity of Great Salt Lake B.K. Baxter, C.D. Litchfield, K. Sowers, J.D. Griffith, P.A. DasSarma S. DasSarma Microbial communitites in the Dead Sea - past, present and future A. Oren, I. Gavrieli, J. Gavrieli, M. Kohen, J. Lati, M. Aharoni Microscopic examination of microbial communitires along a salinity gradient in saltern evaporation poonds: a 'halophilic safari' A. Oren The microbial diversity of a solar saltern on San Francisco Bay C.D. Litchfield, M. Sikaroodi, P.M. Gillivet Diversity of microbial communities: the case of solar salterns C. Pedros-Alio Isolation of viable haloarchaea from ancient salt deposits and application of fluorescent stains for in situ detection of halophiles in hypersaline environmental samples and model fluid inclusions S. Leuko, A. Legat, S. Fendrihan, H. Wieland, C. Radax, C. Gruber, M. Pfaffenhuemer, G. Weidler, H. Stan-Lotter Hydrocarbon degredation under hypersaline conditions. Some facts, some experiments and many open questions H. Patzelt The relevance of halophiles and other extremophiles to Martian and extraterrestrial environments J. Seckbach Halophiles: a terrestrial analog for life in brines on Mars - Halophiles on Mars R.L. Mancinelli SECTION II. ARCHAEA Comparative genomic survey of information transfer systems in two diverse extremely halophilic Archaea, Halobacterium sp. strain NRC-1 and Haloarcula marismortui B.R. Berquist, J. Soneja, S. DasSarma Walsby's square archaeon it's hip to be square but even more hip to be culturable H. Bolhuis Gene regulation and the initiation of translation inhalophilic Archaea F. Pfeifer, P. Zimmermann, S. Scheuch, S. Sartorius-Neef Protein translation, targeting and translocation in Haloferax volcanii J. Eichler, G. Ring, V. Irihimovitch, T. Lichi, I. Tozik, Z. Konrad Enzymes of halophilic Archaea. Recent findings on ureases and nucleoside diphosphate kinases T. Mizuki, R. Usami, M. Kamo, M. Tanokura, M. Kamekura Osmoadaptation in methanogenci Archaea: recent insights from a genomic perspective K. Pfluger, H. Wieland, V. Muller SECTION III. BACTERIA Salinibacter ruber: genomics and biogeography J. Anton, A. Pena, M. Valens, F. Santos, F.-O. Glockner, M. Bauer, J. Dopazo, J. Herrero, R. Rossello-Mora, R. Amann What we can deduce about metabolism in the moderate halophile Chromohalobacter salexigens from its genomic sequence L.N. Csonka, K. O'Connor, F. Larimer, P. Richardson, A. Lapidus, A.D. Ewing, B.W. Goodner, A. Oren K+ transport and its role for osmoregulation in a halophilic memberof the Bacteria domain: characterization of the K+ uptake systems from Halomonas elongate H.-J. Kunte The chloride regulon of Halobacillus halophilus: a novel regulatory network for salt perception and signal transduction in bacteria V. Muller, S.H. Saum Biosynthesis of the compatible solute mannosylglycerate from hyperthermophiles to mesophiles. Genes, enzymes and evolutionary perspectives M.S. da Costa, N. Empadinhas Genes and enzymes of ectoine biosynthesis in the haloalkaliphilic obligate methanotroph 'Methylomicrobium alcaliphilum 20Z' A.S. Reshetnikov, V.N. Khmelenina, I.I. Mustakhimov, Y.V. Ryzhmanova, Y.A. Trotsenko Halophilic Archaea and Bacteria as a source of extracellular hydrolytic enzymes A. Ventosa, C. Sanchez-Porro, S. Martin, E.

Adaptation to life at high salt concentrations in archaea, bacteria, and eukarya

https://mmbr.asm.org/content/mmbr/45/3/462.full.pdf

Adenosine 3',5'-phosphate in fungi.

Low-temperature scanning electron microscopy (LTSEM) involves three main operational phases: 

1.

The specimen is rapidly frozen (“quench-frozen”) after which it is maintained either under vacuum or in a dry, argon atmosphere at a temperature below — 130°C (143K). This is generally considered to be the point above which the recrystallization of pure water will occur (e. g., see Talmon, 1982a, and Read et al., 1983, and references therein). Quench-freezing rapidly transforms freezable cellular and extracellular water into its solid state (ice) and the specimen is considered to be fully frozen-hydrated (FFH).




2.

The FFH specimen may be fractured, dissected, or retained intact and, if required, it may be heated (etched) and/or coated. If the sample is etched, variable amounts of water are removed by sublimation and the specimen may then be considered partially freeze-dried (PFD).




3.

The sample is observed at low temperature [approx. -175°C (98K)] on a temperature-controlled stage in the scanning electron microscope.

Low-Temperature Scanning Electron Microscopy

Models of cell differentiation in conidial fungi.

Localization by X-ray microanalysis of soluble ions, particularly potassium and sodium, in fungal hyphae

Histochemical assays were carried out on mycelium of Dendryphiella salina cultured in media containing either potassium chloride or sea water. Adenosine triphosphatase showed enhanced activity in mycelium from sea-water cultures. The addition of potassium or sodium ions to the assays of material from the potassium chloride cultures also increased this activity. There was less activity in young hyphal tips compared with older areas of the mycelium. These observations help to explain the compartmentation of potassium fluxes in the mycelium of Dendryphiella salina .

Histochemical study of the hyphae and the distribution of adenosine triphosphatase in Dendryphiella salina

l -Sorbose and 3- O -methyl glucose reduce colony diameter and increase the amount of hyphal branching in Dendryphiella salina but have only a small effect on dry weight produced in shake culture. The effect of l -sorbose on colony morphology can be prevented by glucose but not by less readily metabolized carbohydrates. Theophylline and phaseollin act like l -sorbose and 3- O -methyl glucose and there is a synergistic effect between theophylline and the two sugars. Imidazole, cycloheximide and Dio-9 reduce colony diameter but show no paramorphogenic effects. The results are discussed in terms of the removal of glucose repression by cAMP.

Hyphal branching in Dendryphiella salina: Effect of various compounds and the further elucidation of the effect of sorbose and the role of cyclic AMP

A membrane-bound ATPase has been isolated from the marine hyphomycete Dendryphiella salina free of contamination from mitochondria or mitochondrial fragments. The enzyme is activated by magnesium ions and stimulated by both potassium and sodium ions. There is very little synergism between the two cations. The enzyme has an optimum pH of 8.5–9.0 when magnesium ions only are present, and 9.0 when potassium ions are added. Fusicoccin stimulates whilst cyclic AMP inhibits enzyme activity. These two compounds have essentially the reverse effect on the mitochondrial ATPase. The results are discussed in relation to the functioning of the enzyme in the intact hypha.

Mary F.J. Galpin

Papers

Localization by X-ray microanalysis of soluble ions, particularly potassium and sodium, in fungal hyphae

Histochemical study of the hyphae and the distribution of adenosine triphosphatase in Dendryphiella salina

Hyphal branching in Dendryphiella salina: Effect of various compounds and the further elucidation of the effect of sorbose and the role of cyclic AMP

A plasma-membrane ATPase from Dendryphiella salina: Cation specificity and interaction with fusicoccin and cyclic AMP

Potassium and ATPase in Phycomyces