Bacteriophages are an attractive tool for application in the therapy of bacterial infections, for biological control of bacterial contamination of foodstuffs in the alimentary industry, in plant protection, for control of water-borne pathogens, and control of environmental microflora. This review is mainly focused on structures governing phage recognition of host cell and mechanisms of phage adsorption and penetration into microbial cell.

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Bacteriophage receptors, mechanisms of phage adsorption and penetration into host cell.

The still poorly explored world of microbial functioning is about to be uncovered by a combined application of old and new technologies. Bacteria, especially, are still in the dark with respect to their phylogenetic affiliations as well as their metabolic capabilities and functions. However, with the advent of sophisticated flow cytometric and cell sorting technologies in microbiological labs, there is now the possibility to gain this knowledge at the single-cell level without cumbersome cultivation approaches. Cytometry also facilitates the understanding of physiological diversity in seemingly likewise acting populations. Both individuality and diversity lead to the complex and concerted actions of microbial consortia. This review provides an overview of the state of the art in the field. It deals with the handling of microorganisms from the very beginning (i.e. sampling, and detachment and fixation procedures) and goes on to discuss the pitfalls and problems in analysing cells without any further treatment. If information cannot be gained by specific staining procedures, phylogenetic technologies, transcriptomic and proteomic approaches may be options for achieving advanced insights. All in all, flow cytometry will be a mediator technology to gain a deeper insight into the heterogeneity of populations and the functioning of microbial communities.

Functional single-cell analyses: flow cytometry and cell sorting of microbial populations and communities.

https://mmbr.asm.org/content/mmbr/45/3/409.full.pdf

Plasmids, drug resistance, and gene transfer in the genus Streptococcus.

The adhesion of bacteria to surfaces is an ecologically important property which enables them to colonize their natural habitats. Adhesion between bacteria mediated by sex pili and aggregation substances may also promote gene transfers. In this review, we describe the adhesive properties of bacteria (to eukaryotic and prokaryotic cells, and inert surfaces) and emphasize the characteristics of adhesins (structure, function, genetics, and morphology) and their cognate receptors on target surfaces. The physiochemical interactions between bacteria and surfaces can be described by the DLVO theory, but the interaction between bacterial adhesins and their receptor is better described as a ligand receptor interaction. The DLVO theory predicts that no physical contact can occur between bacteria and surface and, hence, predicts that adhesins must be filamentous in order to bridge the space between the two bodies and allow attachment of the bacteria. Adhesins are primarily proteinaceous, although adhesins of streptococci may involve dextrans or lipoteichoic acids. The cognate receptors for adhesins all appear to contain carbohydrates and as such as likely to be glycoconjugates with carbohydrate moieties acting as the receptor sites.

Proteinaceous bacterial adhesins and their receptors

Recent data suggest that, in response to the presence of antibiotics, gene duplication and amplification (GDA) constitutes an important adaptive mechanism in bacteria For example, resistance to sulphonamide, trimethoprim and beta-lactams can be conferred by increased gene dosage through GDA of antibiotic hydrolytic enzymes, target enzymes or efflux pumps Furthermore, most types of antibiotic resistance mechanism are deleterious in the absence of antibiotics, and these fitness costs can be ameliorated by increased gene dosage of limiting functions In this Review, we highlight the dynamic properties of gene amplifications and describe how they can facilitate adaptive evolution in response to toxic drugs

Bacterial gene amplification: implications for the evolution of antibiotic resistance

Purification and biochemical properties of complex flagella isolated from Rhizobium lupini H13-3

The 30 megadalton (Mdal)-conjgaative, fi- plasmid pRSD1 determines inducible tetracycline resistance (Tc) in Escherichia coli. As shown by restriction analysis, a 3.5 Mdal-EcoRI fragment of pRSD1 spliced into the small plasmid pRSD2124 comprises the entire Tc determinant (tet) region. A restriction map of pRSD1 is presented which includes the location of the tet region and of an “underwound” loop not related to Tc (Burkardt et al., 1978). Selective amplification of tet genes is demonstrated by three lines of evidence. (i) The resistance level of cell harbouring pRSD1 increases approximately tenfold by induction with 10μg/ml of tetracycline. Further groth in the presence of 100 μg/ml of the drug (“tet-racycline stress”) selects for cells with even higher resistance levels (about 300 μg/ml) in rec
+ cells. In a recA strain, a smaller proportion of cells attains these high resistance levels suggesting the involvement of host recombination. (ii) Electron micrographs of pRSD1-DNA isolated from tetracycline-stressed cells reveal a heterogeneous population of circular DNA molecules ranging between 1.7 and 21.6 μm. The distribution of contour lengths shows a discrete pattern ascribed to the presence of autonomous single-and multiple-copy Tc determinants and to intact plasmids containing zero to six tet regions in tandem repeats. (iii) This interpretation is supported by heteroduplex and restriction analyses which demonstrate the presence of multiple copies of the 3.5 Mdal-element encompassing the tet region in pRSD1 molecules selected by tetracycline stress. It has been concluded that gene amplification leading to tandem repetition of the tet region ensues in pRSD1. Such plasmids confer increased tetracycline resistance and can, therefore, be selected by high doses of the drug.

Repetition of tetracycline resistance determinant genes on R plasmid pRSD1 in Escherichia coli.

Zellen von Rhizobium lupini H 13-3 besitzen 5–10 peritrich inserierte komplexe Geiseln, deren Feinstruktur durch Hochauflosungs-Elektronenmikroskopie und lichtoptische Diffraktion analysiert wurde. Das Geiselfilament hat einen Durchmesser von 160 A und besteht aus einem zylindrischen Kern (Durchmesser ca. 110 A), der fest von drei Bandern einer helikalen Scheide umgeben ist. Die Scheidenbander sind 49 A breit, durch 49 A-Intervalle voneinander getrennt und haben eine Steigung von 31°. Die komplexen Geiselfilamente bestehen aus einem 43 000-Dalton-Protein, das den Kern und die helikale Scheide aufbaut. Beide gehen ubergangslos aus dem proximalen Geiselhaken hervor, der einen Durchmesser von 150 A und eine Lange von 600 bis 800 A hat. Die Diffraktionsanalyse des Geiselhakens zeigte eine helikale Grundanordnung von globularen Untereinheiten, die ein Oberflachengitter von 5 parallelen Schrauben (Steigung 29° bzw. 33°) bilden, von denen jede fast 11 Untereinheiten pro Helixungang tragt. Die komplexen Geiseln von R. lupini H 13-3 und Pseudomonas rhodos [Schmitt et al.: J. Bact. 117, 844–857 (1974)] sind ein neuer Typ von Bakteriengeiseln. Sie zeigen deutliche Ubereinstimmung in der Feinstruktur, der festen Verbindung von helikaler Scheide und Geiselhaken sowie in der Fragilitat ihrer Filamente; sie unterscheiden sich deutlich im Molekulargewicht der Flagellinmonomeren (43 000 bzw. 55 000). Zellen von R. lupini H 13-3 fuhren schnelle, vibrierende Translationsbewegungen aus. Mogliche Mechanismen der Bewegung komplexer Geiseln werden diskutiert.

Feinstrukturanalyse der komplexen Geißeln von Rhizobium lupini H 13-3

Bacteriophage 7-7-1 is shown to adsorb specifically to the complex flagella of its host Rhizobium lupini H13-3. Deflagellation of motile cells before the addition of phage leads to a complete inhibition of phage propagation for at least 60 min. Among phage-resistant mutants, many non-motile (mot) and non-flagellated (fla) derivatives of R. lupini H13-3 have been selected. Electron microscopic observations indicate that bacteriophage 7-7-1 attaches with its short tail fibres to the conspicuous helical filament of R. lupini flagells. This attachment is reversible; irreversible phage adsorption takes place at the flagellar base. It is postulated that phage 7-7-1 moves along the rotating flagellum towards a final receptor next to the insertion site of the flagellum, where tail contraction and injection of phage nucleic acid occurs.

Bacteriophage 7-7-1 Adsorbs to the Complex Flagella of Rhizobium lupini H13-3

Die Feinstruktur nicht-kontrahierbarer Fimbrien (Pili) der nicht-sternbildenden (sta-) Mutante 3/7 von Pseudomonas echinoides wurde elektronenmikroskopisch untersucht. Hochaufgeloste Aufnahmen negativkontrastierter Fimbrien wurden direkt und mit Hilfe der lichtoptischen Diffraktion analysiert. Die erhaltenen Daten konnen wie folgt zusammengefast werden: Eine sta--Fimbria hat die Gestalt eines Hohlzylinders, dessen Ausendurchmesser 65 A und dessen Innendurchmesser 25 A betragt. Die Zylinderwand besteht aus 3 Schrauben mit gemeinsamer Achse und einer Steigung von ca. 20°. Jede Schraube tragt 6 identische, globulare Untereinheiten pro Umgang. Das Molekulargewicht einer Proteinuntereinheit betragt 8000; dieser Wert wurde durch SDS-Gelelektrophorese mit Standardproteinen bestimmt. Fr bestatigt die elektronenmikroskopisch erhaltenen Strukturparameter, da beide Ergebnisse unabhangig zum gleichen Volumen fur eine Fimbrienuntereinheit fuhren. Aus diesen Daten wurde ein Feinstrukturmodell der sta--Fimbria aufgestellt und seine Ubereinstimmung mit der Originalstruktur durch lichtoptische Diffraktion bestatigt. Dieses Modell wurde ferner zur Deutung der Struktur nicht-kontrahierter Fimbrien des sternbildenden (sta+) Wildtyps benutzt. Ausgehend von dieser Modellvorstellung nicht-kontrahierter sta+-Fimbrien und fruheren Beobachtungen an kontrahierten sta+-Fimbrien (Mayer, 1971), wurde ein Arbeitsmodell fur die Fimbrienkontraktion postuliert.

[Fine structure analysis of fimbria of the starforming soil bacterium Pseudomonas echinoides by electron microscopy, optical diffraction and disc electrophoresis].

Rüdiger Schmitt

Papers

Purification and biochemical properties of complex flagella isolated from Rhizobium lupini H13-3

Repetition of tetracycline resistance determinant genes on R plasmid pRSD1 in Escherichia coli.

Feinstrukturanalyse der komplexen Geißeln von Rhizobium lupini H 13-3

Bacteriophage 7-7-1 Adsorbs to the Complex Flagella of Rhizobium lupini H13-3

[Fine structure analysis of fimbria of the starforming soil bacterium Pseudomonas echinoides by electron microscopy, optical diffraction and disc electrophoresis].