General Microbiology – Roger Y Stanier

(a) A free phage particle with helical tail fibers (Xx 120,000). (b) A phage par- ticle that has adsorbed to a bacterial flagellum, around which the tail fibers are wrapped (c) A group of phage particles attached to several flagella (@®<61,000) SErom™ Be iaeMe Raimondo, N. P. Lundh, and R. J. Martinez, “Primary Ad- sorption Site of Phage PBSI: the Flagellum of Bacillus subtilis,” J. Virol. 2, 256 (1968).

(a) (b) (a) An isolated particle of one of the T-even bacteriophages embedded in phospho- tungstic acid. Note the filled head, contracted sheath, core, and tail fibers. From S. Brenner et al., “Structural Components of Bacteriophage,” J. Mol. Biol. 1, 281 (1959). (b) T-even phage components, with dimensions indicated in nm. From D. E. Bradley, “Ultrastructure of Bacteriophages and Bacteriocins,” Bacteriol.

Revs. 31, 230 (1967). Apical Se * subunits _ Full head JEmety head — Collar Tail fibers Collar =|— Tail fibers extended = contracted (140 x 2) = Sheath ‘ extended ss ed pace pate | End-on view of Tail pins (6) contracted sheath Core (8) / \—Tail pins —__ Unfolded bs tail pins Intact base plate Distended base plate Chap.

12: The Viruses e The formation of “early” proteins y. Tail fiber The syringelike action of the T-even phages. (a) Phage adsorbed to bacterial cell wall; the sheath is extended. (b) The sheath has contracted, driving the tail core through the cell wall. the sheath contracts; the tail core is thus driven through the cell wall (Figure 12.12). When the tip of the core reaches the cell membrane, the DNA contents of the phage head are injected beneath the wall. The syringelike mechanism of the T-even phages is unique; it is not known how the other phages penetrate the cell walls of their hosts or how the DNA of any of the phages penetrates the cell membrane.

The penetration process discovered in the T-even phages, in which the protein capsid is left outside the cell wall, has been assumed to be characteristic of bacteriophages in general. For some phages, however, the penetration mechanism may be quite different. In one group—the filamentous (helical) single-stranded DNA phages—the major protein of the helical capsid penetrates the wall and is deposited on or in the cell membrane; a minor coat protein, called the “A protein,” enters the cytoplasm along with the phage DNA.

Once the phage DNA has reached the host cell cytoplasm, part of it is immediately transcribed by host cell RNA polymerase to form “early” viral messenger RNA. The preexisting ribosomes of the host then translate this viral mRNA to form a complement of new enzymes, including all those necessary for the replication of the phage DNA.

by R. Y. Stainer, M. Doudoroff, E. A. Adelberg All rights reserved. No part of this publication may be reproduced or transmitted, in any form or by any means, without permission. Original American edition published by Prentice-Hall, Inc., Englewood Cliffs, New Jersey, U.S.A. First published in the United Kingdom 1958 Second Edition 1963 Third Edition 1971 Fourth Edition 1977 Published by THE MACMILLAN PRESS LTD London and Basingstoke Associated companies in New York Dublin Melbourne Johannesburg and Madras ISBN 0 333 22013 7 (hard cover) 0 333 22014 5 (paper cover) Printed in Great Britain by Unwin Brothers Limited, Old Woking, Surrey 4 <= S This book is sold subject to the standard conditions of the Net Book Agreement.

The paperback edition of this book is sold subject to the condition that it shall not, by way of trade or otherwise, be lent, resold, hired out, or other- wise circulated without the publisher’s prior consent in any form of binding or cover other than that in which it is published and without a similar condition including this condition being imposed on the subsequent purchaser.

To the memory of Michael Doudoroff (1911-1975).

This is a short excerpt from the opening of “” by Unknown, quoted for review and introduction purposes. All rights belong to the copyright holders.

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