Faculty Opinions recommendation of A single regulatory gene is sufficient to alter bacterial host range.

Phage biology has been developing for the last hundred years, and the potential of phages as tools and treatments has been known since their early discovery. However, the lack of knowledge of the molecular mechanisms coded in phage genomes hindered the development of the field. With current molecular methods, the last decade has been a resurgence of the field. The Special Issue on “Diversity and Evolution of Phage Genomes” is a great example with its 17 manuscripts published. It covers some of the latest methods to sample and characterize environmental and host associated viromes, considering experimental biases and computational developments. Furthermore, the use of molecular tools coupled with traditional methods has allowed to isolate and characterize viruses from different hosts and environments with such diversity that even a new viral class is being proposed. The viruses described cover all different phage families and lifestyles. However, is not only about diversity; the molecular evolution is studied in a set of manuscripts looking at phage-host interactions and their capacity to uncover the frequency and type of mutations behind the bacterial resistance mechanisms and viral pathogenesis, and such methods are opening new ways into identifying potential receptors and characterizing the bacterial host range.

Download Full-text

Bacteriophage-host interaction in the enhanced biological phosphate removing activated sludge system

Water Science & Technology ◽

10.2166/wst.2002.0453 ◽

2002 ◽

Vol 46 (1-2) ◽

pp. 39-43 ◽

Cited By ~ 22

Author(s):

M.A. Khan ◽

H. Satoh ◽

T. Mino ◽

H. Katayama ◽

F. Kurisu ◽

...

Keyword(s):

Activated Sludge ◽

Host Range ◽

Plaque Formation ◽

Complex Interaction ◽

Activated Sludge Process ◽

Bacterial Isolates ◽

Bacterial Host ◽

Microbial Ecosystem ◽

Host Interaction ◽

Range Test

Bacteriophages were isolated from a laboratory scale enhanced biological phosphate removing (EBPR) activated sludge process, and their host range was examined. Bacterial isolates to host the bacteriophages were isolated from the EBPR activated sludge process. Bacteriophages were eluted from the EBPR activated sludge, enriched by incubation with the bacterial isolates, and then tested for plaque formation on each of the bacterial isolates. Out of 12 bacterial isolates isolated, 4 supported plaque formation. Four bacteriophages were obtained from the plaques. The host range test was conducted with the combination of the bacteriophage isolates and the bacterial isolates. Three of the bacteriophages were found to form plaques on more than one host, and one of them formed plaques on both Gram +ve and Gram −ve bacterial isolates. Two of the four bacteriophages failed to form plaques on their original bacterial host, indicating the existence of mutation on either both or one of the host and the bacteriophage. This study strongly suggests that bacteriophages are an active part of the activated sludge microbial ecosystem, having very complex interaction with their host bacteria.

Download Full-text

Molecular analysis of the Rhizobium genes involved in the induction of nitrogen-fixing nodules on legumes

Philosophical Transactions of the Royal Society of London Series B Biological Sciences ◽

10.1098/rstb.1987.0057 ◽

1987 ◽

Vol 317 (1184) ◽

pp. 193-207 ◽

Cited By ~ 5

Keyword(s):

Nitrogen Fixation ◽

Host Range ◽

Symbiotic Nitrogen Fixation ◽

Regulatory Gene ◽

Bacterial Strains ◽

Nod Genes ◽

Aromatic Molecules ◽

Recent Developments ◽

Rhizobium Spp

Recent developments in the molecular genetics of Rhizobium spp . are presented, and the use of mutant bacterial strains to determine which properties are required for symbiotic nitrogen fixation and nodulation of legumes is described. Both the lipopolysaccharide and the exopolysaccharide of Rhizobium spp . are implicated in infection. Recent studies have identified several genes involved in the early steps of this process and in the determination of host-range specificity. Analysis of their products has given some indications of their functions. The expression of most of these nodulation ( nod ) genes is controlled by the regulatory gene nod D, which is itself expressed constitutively, whereas other nod genes are transcribed only when the cells are exposed to compounds present in the rhizosphere of legumes. These compounds were identified as various flavones and flavanones. Other plant-specified aromatic molecules, such as isoflavonoids, antagonize this induction.

Download Full-text

Different impacts of naturally occurring variants of the globally disseminated carbapenemase-encoding plasmid pKpQIL on the biology of host strains

10.1101/495986 ◽

2018 ◽

Author(s):

Howard T. H. Saw ◽

Mark A. Webber ◽

Neil Woodford ◽

Laura J. V. Piddock

Keyword(s):

Escherichia Coli ◽

Klebsiella Pneumoniae ◽

Host Range ◽

Generation Time ◽

Enterobacter Cloacae ◽

Bacterial Host ◽

E Coli ◽

Naturally Occurring ◽

Filter Mating ◽

Host Strains

SynopsisKlebsiella-associated plasmid pKpQIL and its variant have been isolated globally. Our study aimed to determine whether a naturally occurring variant has altered host range and impacts on the fitness of different bacterial host strains. The plasmids pKpQIL-UK and pKpQIL-D2 were transferred from the original clinical isolate host strains of Klebsiella pneumoniae into Escherichia coli, Salmonella Typhimurium, Enterobacter cloacae and Serratia marcescens strains by filter-mating and conjugation frequencies determined and compared. The fitness of the resulting transconjugants was assessed by determining growth kinetics, ability to form a biofilm and persistence of the plasmids in each host was also measured. Transfer of either plasmid into Salmonella and S. marcescens was similar. However, pKpQIL-UK transferred into E. coli at a higher rate than did pKpQIL-D2; the reverse was found for E. cloacae. Both plasmids were rapidly lost from the E. coli population. Plasmid pKpQIL-UK, but not -D2, was able to persist in Salmonella. Although pKpQIL-UK imposed a greater fitness cost (inferred from an increased generation time) than -D2 on E. cloacae, it was able to persist as well as pKpQIL-D2 in this host. The pKpQIL-D2 plasmid did not confer any fitness benefit on any of the hosts under the conditions tested. Variants of the globally important pKpQIL plasmid have arisen in patients due to recombination. The impacts of the pKpQIL-UK plasmid and the -D2 variant in various Enterobacteriaceae are host-dependent. Continuing evolution of pKpQIL may alter its host range in the future.

Download Full-text

The incN antibiotic-resistance plasmid pCU1: bacterial host-range, nucleotide sequence, deletion and subcloning analysis of the replicon.

10.22215/etd/1990-01652 ◽

1990 ◽

Author(s):

B. Krishnan

Keyword(s):

Antibiotic Resistance ◽

Nucleotide Sequence ◽

Host Range ◽

Bacterial Host ◽

Resistance Plasmid ◽

Sequence Deletion

Download Full-text

ON SOME GENETIC ASPECTS OF PHAGE Λ RESISTANCE IN E. COLI K12

Genetics ◽

10.1093/genetics/71.2.207 ◽

1972 ◽

Vol 71 (2) ◽

pp. 207-216

Author(s):

J P Thirion ◽

M Hofnung

Keyword(s):

Growth Rate ◽

Host Range ◽

Genetic Map ◽

Regulatory Gene ◽

E Coli ◽

Maltose Metabolism ◽

Oligomeric Protein

ABSTRACT Most mutations rendering E. coli K12 resistant to phage λ, map in two genetic regions mal A and mal B.—The malB region contains a gene lamB specifically involved in the λ receptor synthesis. Twenty-one independent lamB mutations studied by complementation belonged to a single cistron. This makes it very likely that lamB is monocistronic. Among the lamB mutants some are still sensitive to a host range mutant of phage λ. Mutations mapping in a proximal gene essential for maltose metabolism inactivate gene lamB by polarity confirming that both genes are part of the same operon. Because cases of intracistronic complementation have been found, the active lamB product may be an oligomeric protein.—Previously all λ resistant mutations in the malA region have been shown to map in the malT cistron. malT is believed to be a positive regulatory gene necessary for the induction of the "maltose operons" in the malA region and in the malB region of the E. coli K12 genetic map. No trans dominant malT mutation have been found. Therefore if they exist, they occur at a frequency of less than 10–8, or strongly reduce the growth rate of the mutants.

Download Full-text

The saccharibacterium TM7x elicits differential responses across its host range

The ISME Journal ◽

10.1038/s41396-020-00736-6 ◽

2020 ◽

Vol 14 (12) ◽

pp. 3054-3067 ◽

Cited By ~ 2

Author(s):

Daniel R. Utter ◽

Xuesong He ◽

Colleen M. Cavanaugh ◽

Jeffrey S. McLean ◽

Batbileg Bor

Keyword(s):

Host Range ◽

Growth Dynamics ◽

Comparative Genomic ◽

Bacterial Host ◽

Genomic Features ◽

Initial Infection ◽

Symbiotic Interactions ◽

Ideal System ◽

Genomic Analyses ◽

Crash Recovery

Abstract Host range is a fundamental component of symbiotic interactions, yet it remains poorly characterized for the prevalent yet enigmatic subcategory of bacteria/bacteria symbioses. The recently characterized obligate bacterial epibiont Candidatus Nanosynbacter lyticus TM7x with its bacterial host Actinomyces odontolyticus XH001 offers an ideal system to study such a novel relationship. In this study, the host range of TM7x was investigated by coculturing TM7x with various related Actinomyces strains and characterizing their growth dynamics from initial infection through subsequent co-passages. Of the twenty-seven tested Actinomyces, thirteen strains, including XH001, could host TM7x, and further classified into “permissive” and “nonpermissive” based on their varying initial responses to TM7x. Ten permissive strains exhibited growth/crash/recovery phases following TM7x infection, with crash timing and extent dependent on initial TM7x dosage. Meanwhile, three nonpermissive strains hosted TM7x without a growth-crash phase despite high TM7x dosage. The physical association of TM7x with all hosts, including nonpermissive strains, was confirmed by microscopy. Comparative genomic analyses revealed distinguishing genomic features between permissive and nonpermissive hosts. Our results expand the concept of host range beyond a binary to a wider spectrum, and the varying susceptibility of Actinomyces strains to TM7x underscores how small genetic differences between hosts can underly divergent selective trajectories.

Download Full-text