Factors affecting phage D29 infection: a tool to investigate different growth states of mycobacteria

Bacteriophages D29 and TM4 are able to infect a wide range of mycobacteria, including pathogenic and non-pathogenic species. Successful phage infection of both fast- and slow-growing mycobacteria can be rapidly detected using the phage amplification assay. Using this method, the effect of oxygen limitation during culture of mycobacteria on the success of phage infection was studied. Both D29 and TM4 were able to infect cultures of M. smegmatis and Mycobacterium avium subspecies paratuberculosis (MAP) grown in liquid with aeration. However when cultures were grown under oxygen limiting conditions, only TM4 could productively infect the cells. Cell attachment assays showed that D29 could bind to the cells surface but did not complete the lytic cycle. The ability of D29 to productively infect the cells was rapidly recovered (within 1 day) when the cultures were returned to an aerobic environment and this recovery required de novo RNA synthesis. These results indicated that under oxygen limiting conditions the cells are entering a growth state which inhibits phage D29 replication, and this change in host cell biology which can be detected by using both phage D29 and TM4 in the phage amplification assay.

Cluster K mycobacteriophages: insights into the evolutionary origins of mycobacteriophage TM4

Five newly isolated mycobacteriophages –Angelica, CrimD, Adephagia, Anaya, and Pixie – have similar genomic architectures to mycobacteriophage TM4, a previously characterized phage that is widely used in mycobacterial genetics. The nucleotide sequence similarities warrant grouping these into Cluster K, with subdivision into three subclusters: K1, K2, and K3. Although the overall genome architectures of these phages are similar, TM4 appears to have lost at least two segments of its genome, a central region containing the integration apparatus, and a segment at the right end. This suggests that TM4 is a recent derivative of a temperate parent, resolving a long-standing conundrum about its biology, in that it was reportedly recovered from a lysogenic strain of Mycobacterium avium, but it is not capable of forming lysogens in any mycobacterial host. Like TM4, all of the Cluster K phages infect both fast- and slow-growing mycobacteria, and all of them – with the exception of TM4 – form stable lysogens in both Mycobacterium smegmatis and Mycobacterium tuberculosis; immunity assays show that all five of these phages share the same immune specificity. TM4 infects these lysogens suggesting that it was either derived from a heteroimmune temperate parent or that it has acquired a virulent phenotype. We have also characterized a widely-used conditionally replicating derivative of TM4 and identified mutations conferring the temperature-sensitive phenotype. All of the Cluster K phages contain a series of well conserved 13 bp repeats associated with the translation initiation sites of a subset of the genes; approximately one half of these contain an additional sequence feature composed of imperfectly conserved 17 bp inverted repeats separated by a variable spacer. The K1 phages integrate into the host tmRNA and the Cluster K phages represent potential new tools for the genetics of M. tuberculosis and related species.

Improved contamination control for a rapid phage-based rifampicin resistance test for Mycobacterium tuberculosis

A prospective study was conducted of the rapid FASTPlaque-Response test for determination of rifampicin resistance in Mycobacterium tuberculosis with and without the addition of an antimicrobial supplement containing nystatin, oxacillin and aztreonam (NOA) to control specimen-related contamination. A total of 631 smear-positive sputum specimens was tested. The age of specimens ranged from 0 to 21 days. The NOA antimicrobial was effective at controlling contamination, with 4.1 % of specimens contaminated when the NOA antimicrobial supplement was used compared with 13.9 % contamination without NOA. Overall levels of interpretability of the test with NOA were 87.8 % with specimens of < or =3 days and 79.0 % for all specimens. This compared with 70.1 and 73.8 % readable results, respectively, from conventional culture-based drug susceptibility testing (DST). Sensitivity, specificity and overall accuracy of the FASTPlaque-Response test for rifampicin resistance were 98.1, 96.3 and 96.6 %, respectively, for all specimens with NOA, and 93.2, 96.3 and 95.9 % without NOA, when compared with resolved conventional DST results. Inclusion of the NOA supplement reduced contamination, increased the number of interpretable results and did not adversely affect the performance of the FASTPlaque-Response test. Thus, the use of NOA improves the robustness of the test, facilitating its wider implementation.

UV light inactivation of Mycobacterium avium subsp. paratuberculosis in milk as assessed by FASTPlaqueTB phage assay and culture

UV light inactivation of Mycobacterium avium subsp. paratuberculosis in Middlebrook 7H9 broth and whole and semiskim milk was investigated using a laboratory-scale UV machine that incorporated static mixers within UV-penetrable pipes. UV treatment proved to be less effective in killing M. avium subsp. paratuberculosis suspended in milk (0.5- to 1.0-log(10) reduction per 1,000 mJ/ml) than that suspended in Middlebrook 7H9 broth (2.5- to 3.3-log(10) reduction per 1,000 mJ/ml). The FASTPlaqueTB phage assay provided more rapid enumeration of surviving M. avium subsp. paratuberculosis (within 24 h) than culture on Herrold's egg yolk medium (6 to 8 weeks). Despite the fact that plaque counts were consistently 1 to 2 log(10) lower than colony counts throughout the study, UV inactivation rates for M. avium subsp. paratuberculosis derived using the phage assay and culture results were not significantly different (P = 0.077).

The G23 and G25 Genes of Temperate Mycobacteriophage L1 Are Essential for The Transcription of Its Late Genes

Two lysis-defective but DNA synthesis non-defective temperature-sensitive (ts) mutants of mycobacteriophage L1, L1G23ts23 and L1G25ts889 were found to be defective also in phage-specific RNA synthesis in the late period of their growth at 42 degrees C, each to the extent of 50% of that at 32 degrees C. The double mutant, L1G23ts23G25ts889 showed the ts defect in phage RNA synthesis that was nearly additive of those shown individually by the two single-mutant parents. Both G23 and G25 were shown to start functioning sometimes between 30 and 45 min after infection but the former gene might be dispensable after 45 min, while the latter was not. Northern analysis also shows that at 42 degrees C, L1G23ts23 affects RNA synthesis more strongly than L1G25ts889 from L1 DNA segments that serve as the template for late gene transcription. Among the 21 virion and 12 non-virion late proteins synthesized by L1, L1G23ts23 is defective in the synthesis of at least 9 virion and all of non-virion proteins at 42 degrees C. In contrast, L1G25ts889 is completely defective in synthesis of all the 33 late proteins. Possible roles of G23 and G25 in the positive regulation of transcription of different sets of late genes of L1 have been discussed.

Evaluation of rifampicin and isoniazid susceptibility testing of Mycobacterium tuberculosis by a mycobacteriophage D29-based assay

Conventional methods for determining drug susceptibility of Mycobacterium tuberculosis require several weeks to obtain results, limiting their usefulness; automated methods and those based on molecular biology techniques have been able to reduce the turnaround time, but their high cost and need for sophisticated equipment restrict their use in developing countries. The goal of the present study was to evaluate the diagnostic accuracy of a rapid (3-4 days) low-cost test based on the use of mycobacteriophage D29 to determine the susceptibility of strains of M. tuberculosis to rifampicin (RIF) and isoniazid (INH). Results obtained show that susceptibility testing for RIF has a high diagnostic accuracy as compared to the standard indirect proportion method on Löwenstein-Jensen medium (sensitivity 100% and specificity 98%). Given the association between the resistance to RIF and INH, which define multidrug resistance (MDR), this test seems suitable for rapid detection of MDR tuberculosis strains (kappa=0.978). Susceptibility testing for INH using mycobacteriophage D29 had a good but lower diagnostic accuracy as compared to the standard method (sensitivity 80.4% and specificity 80.8%); the test would then be of limited usefulness in the management of tuberculosis patients. Further studies to determine the relationship of mycobacteriophage D29 tests to in vivo correlates of sensitivity to specific antituberculosis drugs are warranted.

Development of a new, combined rapid method using phage and PCR for detection and identification of viable Mycobacterium paratuberculosis bacteria within 48 hours

The FASTPlaqueTB assay is an established diagnostic aid for the rapid detection of Mycobacterium tuberculosis from human sputum samples. Using the FASTPlaqueTB assay reagents, viable Mycobacterium avium subsp. paratuberculosis cells were detected as phage plaques in just 24 h. The bacteriophage used does not infect M. avium subsp. paratuberculosis alone, so to add specificity to this assay, a PCR-based identification method was introduced to amplify M. avium subsp. paratuberculosis-specific sequences from the DNA of the mycobacterial cell detected by the phage. To give further diagnostic information, a multiplex PCR method was developed to allow simultaneous amplification of either M. avium subsp. paratuberculosis or M. tuberculosis complex-specific sequences from plaque samples. Combining the plaque PCR technique with the phage-based detection assay allowed the rapid and specific detection of viable M. avium subsp. paratuberculosis in milk samples in just 48 h.

A peptidoglycan hydrolase motif within the mycobacteriophage TM4 tape measure protein promotes efficient infection of stationary phase cells

The predominant morphotype of mycobacteriophage virions has a DNA-containing capsid attached to a long flexible non-contractile tail, features characteristic of the Siphoviridae. Within these phage genomes the tape measure protein (tmp) gene can be readily identified due to the well-established relationship between the length of the gene and the length of the phage tail--because these phages typically have long tails, the tmp gene is usually the largest gene in the genome. Many of these mycobacteriophage Tmp's contain small motifs with sequence similarity to host proteins. One of these motifs (motif 1) corresponds to the Rpf proteins that have lysozyme activity and function to stimulate growth of dormant bacteria, while the others (motifs 2 and 3) are related to proteins of unknown function, although some of the related proteins of the host are predicted to be involved in cell wall catabolism. We show here that motif 3-containing proteins have peptidoglycan-hydrolysing activity and that while this activity is not required for phage viability, it facilitates efficient infection and DNA injection into stationary phase cells. Tmp's of mycobacteriophages may thus have acquired these motifs in order to avoid a selective disadvantage that results from changes in peptidoglycan in non-growing cells.

Usefulness of a new mycobacteriophage-based technique for rapid diagnosis of pulmonary tuberculosis

A new mycobacteriophage-based technique (PhageTek MB) was compared with standard culture and staining techniques for diagnosis of pulmonary tuberculosis. A total of 2,048 respiratory specimens from 1,466 patients collected from February 2000 to March 2001 were studied by both (i) conventional methods (direct microscopic examination [auramine-rhodamine fluorochrome], and culture in BacT/ALERT 3D and solid media) and (ii) the PhageTek MB assay. This phenotypic test utilizes specific mycobacteriophages to detect the presence of live Mycobacterium tuberculosis complex organisms within a decontaminated clinical sample. Overall, 205 (10%) specimens were positive for mycobacteria (134 patients): 144 (70.2%) M. tuberculosis isolates and 61 (29.8%) nontuberculous mycobacterium isolates (30 Mycobacterium kansasii, 12 Mycobacterium xenopi, 9 Mycobacterium gordonae, 7 Mycobacterium avium complex, 2 Mycobacterium chelonae, and 1 Mycobacterium fortuitum isolate). PhageTek MB was more likely to give a positive result with specimens in which high numbers of acid-fast bacilli were observed on the smear. The sensitivity, specificity, and positive and negative predictive values of this mycobacteriophage-based technique versus culture for M. tuberculosis were 58.3, 99.1, 83.2, and 96.9%, respectively. PhageTek MB is a rapid (48-h), specific, safe, and easy-to-perform test. According to the prevalence of the disease in the population studied, the test would require improved sensitivity in order to be used as a screening test for routine diagnosis of respiratory tuberculosis in our setting.

Evaluation of a rapid bacteriophage-based method for the detection of Mycobacterium tuberculosis in clinical samples

Rapid, sensitive and low-cost methods are needed urgently for the detection of Mycobacterium tuberculosis in clinical samples, especially in developing countries. To this end, the clinical performance of FASTPlaqueTB(TM) (a bacteriophage-based method) has been studied in parallel with microscopy, standard microbiological culture and in-house IS6110-based PCR methods. A total of 64 samples, including 42 sputum samples and 22 urine samples, were tested in this study. The sensitivity, specificity and overall accuracy values for the FASTPlaqueTB assay relative to that of culture were respectively 76.5, 95 and 90 %. The corresponding values for the in-house IS6110-based PCR assay were 88, 91 and 90 % and, for Ziehl-Neelsen staining, were 59, 95 and 85 %. FASTPlaqueTB gave better clinical performance with urine samples than with sputum samples (sensitivity, specificity and overall accuracy were 100 % with urine samples and 64, 93 and 84 % with sputum samples). The 100 % sensitivity of FASTPlaqueTB was higher than that of the corresponding values for PCR (67 %) with urine samples. In conclusion, FASTPlaqueTB proved to be sensitive, cheap relative to the PCR and rapid. It is able to detect M. tuberculosis in clinical samples within 1 day, reducing the time to diagnosis in comparison with culture.

A high yielding mutant of mycobacteriophage L1 and its application as a diagnostic tool

L1 is a lysogenic phage of mycobacteria, which along with L5 and D29 constitute a closely linked family of homoimmune mycobacteriophages. These phages can be potentially used for genetic engineering of mycobacteria and diagnosis of mycobacterial infection. The effectiveness of such phage based systems depends on the efficiency with which they infect and grow within target cells. While working with phage L1c1ts which is a temperature sensitive mutant of phage L1, we observed that high yielding phage stocks were generated by repeated passage through the host, Mycobacterium smegmatis. A plaque purified mutant L1-P2, obtained from one such high yielding stock, when analyzed further was found to infect host cells with increased efficiency. The DNA obtained from L1-P2 was examined by restriction digestion, and it was observed that spontaneous loss of DNA fragment from the right arm, which encodes early regulatory factors, had occurred. It has been further demonstrated that the high yielding property of the mutant phage could be utilized to increase the sensitivity of mycobacteriophage-based detection systems.

Identification of an early positive regulatory gene of mycobacteriophage L1

Among 14 temperature-sensitive, growth-defective mutants of mycobacteriophage L1 showing a lysis-defective phenotype at 42 degrees C, six are, in addition, defective in phage DNA synthesis at 42 degrees C. In the present study, we show that one of the latter six mutants, L1G27ts901, is also defective in the synthesis of both an L1-specific exonuclease (a representative delayed early protein), and of RNA in both the delayed early and late periods but not in the immediate early period. The results of a temperature-shift experiment suggest that the synthesis of L1 exonuclease is regulated by G27 at the level of transcription. Furthermore, the temperature-sensitive defect in delayed early and late RNA synthesis could be largely overcome when the L1G27ts901-infected culture was shifted from 32 to 42 degrees C at 10 min but not at zero time post-infection. These results suggest that the primary effect of the G27ts901 mutation is to make the phage defective in transcription of delayed early genes at 42 degrees C, and the defect in late RNA synthesis by this mutant is a secondary effect which is caused by its inability to express regulatory gene products. We conclude that G27 is involved in the positive regulation of expression of the delayed early genes of L1 at the transcriptional level.

A Mycobacterium smegmatis mutant with a defective inositol monophosphate phosphatase gene homolog has altered cell envelope permeability

A bacteriophage infection mutant (strain LIMP7) of Mycobacterium smegmatis was isolated following transposon mutagenesis. The mutant showed an unusual phenotype, in that all phages tested produced larger plaques on this strain compared to the parent strain. Other phenotypic characteristics of the mutant were slower growth, increased clumping in liquid culture, increased resistance to chloramphenicol and erythromycin, and increased sensitivity to isoniazid and several beta-lactam antibiotics. Permeability studies showed decreases in the accumulation of lipophilic molecules (norfloxacin and chenodeoxycholate) and a small increase with hydrophilic molecules (cephaloridine); taken together, these characteristics indicate an altered cell envelope. The DNA adjacent to the transposon in LIMP7 was cloned and was shown to be highly similar to genes encoding bacterial and mammalian inositol monophosphate phosphatases. Inositol is important in mycobacteria as a component of the major thiol mycothiol and also in the cell wall, with phosphatidylinositol anchoring lipoarabinomannan (LAM) in the cell envelope. In LIMP7, levels of phosphatidylinositol dimannoside, the precursor of LAM, were less than half of those in the wild-type strain, confirming that the mutation had affected the synthesis of inositol-containing molecules. The impA gene is located within the histidine biosynthesis operon in both M. smegmatis and Mycobacterium tuberculosis, lying between the hisA and hisF genes.

Mycobacteriophage D29 contains an integration system similar to that of the temperate mycobacteriophage L5

A mycobacteriophage D29 DNA fragment cloned in pRM64, a shuttle plasmid that transforms Mycobacterium smegmatis, was sequenced. The determined sequence was 2592 nucleotides long and had a mean G+C content of 63.7 mol%, similar to that of mycobacterial DNA. Four ORFs were identified: one with strong homology to dCMP deaminase genes; one homologous to mycobacteriophage L5 gene 36, whose function is unknown; one encoding a possible excisase; and one encoding an integrase. The intergenic region between the putative excisase gene and the integrase gene had a lower than average G+C content and showed the presence of the same attP core sequence as mycobacteriophage L5. Transformation experiments using subclones of pRM64 indicated that the integrase gene and all the intergenic region were essential for stable transformation. A subclone containing the integrase gene and the core attP sequence was able to transform but recombinants were highly unstable. Southern analysis of total DNA from cells transformed with pRM64 and its derivatives showed that all the plasmids were integrated at one specific site of the bacterial chromosome. A recombinant exhibiting a high level of resistance to the selective drug kanamycin had two plasmids integrated at different sites. These results demonstrated that the D29 sequences contained in pRM64 were integrative, indicating that the generally hold view of D29 as a virulent phage must be reviewed.

Construction of D29 shuttle phasmids and luciferase reporter phages for detection of mycobacteria

Diseases caused by Mycobacterium tuberculosis, M. leprae and M. avium, cause significant morbidity and mortality worldwide. Effective treatments require that the organisms be speciated and that drug susceptibilities for the causative organisms be characterized. Reporter phage technology has been developed as a rapid and convenient method for identifying mycobacterial species and evaluating drug resistance. In this report we describe the construction of luciferase reporter phages from mycobacteriophage D29 DNA. Shuttle phasmids were first constructed with D29 in order to identify non-essential regions of the D29 genomes and to introduce unique cloning sites within that region. Using this approach, we observed that all of the D29 shuttle phasmids had the cosmid vector localized to one area of the phage genome near one cohesive end. These shuttle phasmids had been constructed with a cosmid that could be readily excised from the D29 genome with different sets of restriction enzymes. Luciferase reporter phages were made by substituting the luciferase cassette for the cosmid vector. Recombinant phages with the luciferase cassette fall into two groups. One group produced light and had the expression cassette oriented with the promoter directing transcription away from the cohesive end. In contrast, the other group had the expression cassette in the opposite orientation and failed to produce light during lytic infection, but did produce light in L5 lysogens which are known to repress D29 promoters. These results suggest that a phage promoter of the D29 phage can occlude the expression of a promoter introduced into this region. D29 luciferase reporter phages are capable of detecting low numbers of L5 lysogens like L5 luciferase phages. However, unlike L5 luciferase phages, D29 luciferase phages can readily infect M. tuberculosis and M. bovis BCG, demonstrating that these phages can be used to evaluate drug susceptibilities of many types of mycobacteria.

L5 luciferase reporter mycobacteriophages: a sensitive tool for the detection and assay of live mycobacteria

Recombinant bacteriophages provide efficient delivery systems for introducing reporter genes into specific bacterial hosts. We have constructed mycobacteriophage L5 recombinants carrying the firefly luciferase gene inserted into the tRNA region of the phage genome. Infection of Mycobacterium smegmatis by these phages results in expression of the luciferase gene and light emission. Fortuitously, the luciferase gene is expressed continuously in lysogens surviving infection. Synthesis of luciferase from a mycobacterial promoter created by cloning enables the detection of extremely small numbers of M. smegmatis cells. These reporter phages can be used to discriminate between drug-sensitive and drug-resistant strains of M. smegmatis, and may provide tools for the rapid identification and classification of antimycobacterial agents.

New pyruvylated, glycosylated acyltrehaloses from Mycobacterium smegmatis strains, and their implications for phage resistance in mycobacteria

Phage resistance and apparent lysogenization of Mycobacterium smegmatis due to infection with mycobacteriophage D29 results in the emergence of new variations of the pyruvylated, acylated trehaloses described by Saadat and Ballou, J. Biol. Chem. 258 (1983) 1813-1818. Thin-layer chromatography of the glycolipids from two strains of phage-resistant M. smegmatis (mc(2)22 and mc(2)11) and comparison with those from phage-sensitive strains revealed a new, more mobile glycolipid in each case. The structures of these acyltrehalose-containing lipooligosaccharides were elucidated by a combination of gas-liquid chromatography-mass spectrometry, methylation analysis, 1H and 13C NMR spectroscopy, and fast-atom bombardment mass spectrometry. The glycolipid from M. smegmatis mc(2)22 is beta-D-Glcp-(1-->3)-4,6-O-(1-methoxycarbonylethylidene)-beta-D-Glc p-(1-->4)- beta-D-Glcp-(1-->6)-2-O-acyl-alpha-D-Glcp-(<==>1)-3,4-O-acyl-alpha-D-Glc p and that from M. smegmatis mc(2)11 is 4,6-O-(1-methoxycarbonylethylidene)-3-O-Me-beta-D-Glcp-(1-->3)-4,6 -O- (1-methoxycarbonylethylidene)-beta-D-Glcp-(1-->4)-beta-D-Glcp-(1-- >6)-2-O-acyl- alpha-D-Glcp-(1<==>1)-3,4-di-O-acyl-alpha-D-Glcp. These differ from the original pyruvylated glycolipids of Saadat and Ballou in the extent of their O-acylation and O-methylation. The findings are the first example of the definition of a chemical basis for phage resistance and presumed lysogeny in mycobacteria, and show parallels to related changes in gram-negative enteric bacteria.

Isolation, characterization, and mapping of temperature-sensitive mutations in the genes essential for lysogenic and lytic growth of the mycobacteriophage L1

Forty temperature-sensitive mutations affecting lytic growth and eight affecting both establishment and maintenance of lysogeny of the temperate mycobacteriophage L1 have been isolated. All of the latter mutations form one complementation group and map within a very short region around the 15% coordinate of the L1 genome; these affect a single gene, cl, coding for the L1 repressor. The former 40 mutations form 28 complementation groups, identifying 28 different genes, G1-G28, essential for the lytic growth of L1. These genes have been mapped using the Gts mutations. Of the 28 Gts mutants, 14 are defective in host lysis at 42 degrees but not at 32 degrees while the other 14 can lyse the host at both temperatures. Among the former 14 Gts mutants, 6 are also defective in L1 DNA synthesis at 42 degrees, and they map in two different clusters, 4 around 65% and 2 around 84% of the L1 genome.

Superinfection immunity of mycobacteriophage L5: applications for genetic transformation of mycobacteria

Mycobacteriophage L5 is a temperate phage of the mycobacteria that forms stable lysogens in Mycobacterium smegmatis. We show here that the 183-amino-acid product of L5 gene 71 confers immunity to L5 superinfection, is required for maintenance of the lysogenic state and contains a helix-turn-helix DNA-binding motif--properties associated with repressors of temperate phages. We have utilized these observations to demonstrate the use of L5 gene 71 as a selectable marker for genetic transformation of the mycobacteria. Significantly, the use of L5 gene 71 as a selectable gene avoids the requirement for antibiotic-resistance genes providing an important tool for manipulation of the pathogens Mycobacterium tuberculosis and Mycobacterium avium, and for the construction of recombinant BCG vaccines.

Action of colistin (polymyxin E) on the lytic cycle of the mycobacteriophage D29 in Mycobacterium tuberculosis

The antibiotic colistin (polymyxin E) inhibited the lytic cycle of the mycobacteriophage D29 in the tubercle bacilli, but not the D29 adsorption. The protein and nucleic acid synthesis in D29-infected bacteria were not affected significantly. The inhibitory activity was reversed by washing off the antibiotic, and by addition of Ca++, but not in media made iso-osmotic by addition of NaCl or sucrose. Transmission electron microscopy revealed an asymmetric to symmetric transition in the staining profile of the cytoplasmic membrane. Though no mature phage particles were ever observed in colistin-treated, D29-infected tubercle bacilli, loosely arranged aggregates resembling phage proheads were occasionally found. Judging from the above data, it was concluded that colistin inhibited D29 lytic cycle by causing molecular displacements in the inner leaflet of the cytoplasmic membrane, and consequently, the binding sites for D29 structural proteins were not available.

Abortive infection of Mycobacterium leprae by the mycobacteriophage D29

The interactions of mycobacteriophage D29 and Mycobacterium leprae were examined. It was demonstrated that after adsorption D29 injected its DNA in M. leprae. While the synthesis of host proteins and lipids were inhibited in M. tuberculosis and in M. smegmatis during infection by D29, the results were inconclusive in the case of M. leprae because these bacteria did not incorporate the appropriate substrates.

Induction of bacteriophage from members of the Mycobacterium avium, Mycobacterium intracellulare, Mycobacterium scrofulaceum serocomplex

Bacteriophages have been induced from strains in the Mycobacterium avium, Mycobacterium intracellulare, Mycobacterium scrofulaceum serocomplex by exposure of cultures to UV light or treatment with mitomycin C. One-sixth of the strains examined, representing all but one of the 31 authenticated serotypes, were found to possess phages lytic for a Mycobacterium smegmatis indicator strain. Four single-plaque isolated phages, TM4, TM9, TM10 and TM20, were purified and shown to have a similar morphology on electron micrographs. They had an isometric head of diameter 50-58 nm and a flexible non-contractile tail about 170 nm in length with a terminal bulb. All had an identical buoyant density in CsCl of 1.521 g cm-3 and extreme sensitivity to chloroform. The induced phages differed in host range and possessed the unique ability to lyse other members of the serocomplex. Interest in these phages centres on a possible role in mediating genetic interrelationships between members of the serocomplex.

Presence of lipids in mycobacteriophage i3

The presence of lipids has been demonstrated in mycobacteriophage I3. The total lipid was composed of 69% phospholipids and 31% neutral lipids. More than two-thirds of phospholipids present in the phage were synthesized in the host prior to infection. The fatty acid composition of the phage differed markedly from that of its host, both in chain length and the degree of saturation. The phage lipid was mostly composed of saturated fatty acids of which more than 50% were short chain fatty acids. Changes in growth temperatures reflected variations in fatty acid composition, characteristic of the phage, and which were distinctly different from those of the host. Electron microscopic observations revealed that the phage has a membranous bilayer structure. The presence of lipids may facilitate the phage-host interaction especially in lipid-rich organisms like mycobacteria.

Effects of antituberculosis and antileprosy drugs on mycobacteriophage D29 growth

The minimal inhibitory concentrations of antituberculosis and antileprosy drugs were determined for Mycobacterium aurum. The concentrations that reduced the final yield of bacteriophage D29R1 by 50% and the time during the replication cycle at which the drugs completely inhibited phage production were estimated. THe 50% inhibitory concentration/minimal inhibitory concentration ratios were close to 1.0 for clofazimine, colistin, rifampin, and streptomycin; these ratios were high for dapsone (diaminodiphenylsulfone) and isoniazid. Ethambutol (minimal inhibitory concentration, 1.0 micrograms/ml) was without effect on viral growth.

Requirement for calcium ions in mycobacteriophage I3 DNA injection and propagation

Ca2+ ions are absolutely necessary for the propagation of mycobacteriophage I3 in synthetic medium. These ions are required for successful infection of the host and during the entire span of the intracellular development of the phage. A direct assay of the phage DNA injection using 32[P] labelled phage, shows that Ca2+ ions are necessary for the injection process. The injection itself is a slow process and takes 15 min to complete at 37 degrees C. The bacteria infected in presence of Ca2+ tend to abort if the ions are subsequently withdrawn from the growth medium. The effect of calcium withdrawal is maximally felt during the early part of the latent period; however, later supplementation of Ca2+ ions salvage phage production and the mature phage progeny appear after a delayed interval, proportional to the time of addition of Ca2+.

Resistance relationships in Mycobacterium smegmatis ATCC 607 to phages sensitive or resistant to both chloroform and streptomycin sulphate

Four of eight mycobacteriophages did not form plaques after they were exposed to chloroform. Phages sensitive to chloroform did not produce plaques when plated on media containing 1000 microgram/ml of streptomycin sulphate. The same concentration of dihydrostreptomycin sulphate did not interfere with plaque formation. Mutants of Mycobacterium smegmatis resistant to each of the eight phages were isolated. Sensitivity or resistance to chloroform and streptomycin sulphate and phage resistant bacterial mutants may provide a basis for classifying the mycobacteriophages.

Comparison of several culture media used for studies on mycobacteriophages

The value of RVA, N-1, 7H10, 7H11 and Sauton's media for studies on mycobacteriophage infeciton and lysis of mycobacteria was assessed. Experiments were made with mycobacteriophages BGI, BKI, CRI-3, G37, and LG, all of which lyse Mycobacterium smegmatis strain 607B, and with mycobacteriophage DS6A which lyses Mycobacterium tuberculosis strain H37Rv. The methods involved "direct lysis", the measurement of "routine test dilutions" and counts of plaque-forming units. It was found that N-1, 7H10 and 7H11 media gave better overall results than RVA medium for M. smegmatis strain 607B and its phages, and that RVA medium was generally the most useful for M. tuberculositems employed.

Biochemical and morphological characterization of mycobacteriophage R1

Large-scale propagation of mycobacteriophage R1 in broth culture has allowed the isolation of quantities of virus sufficient for characterization of its nucleic acid and lipid components as well as investigation of its ultrastructural attributes. Analysis of R1 DNA indicates that it is double stranded and possesses a molecular weight of 2.5 X 10(7) and a guanine-plus-cytosine content of 65.7 +/- 0.5%. The lipid fraction of R1 accounts for 14% of the total dry weight of the virus, 20% of which was identified as free or esterified sterols. A rapid loss of viral titer occurred after seconds of exposure to organic solvents. This result suggests that the lipid fractions of R1 is essential for its infectivity. Electron microscopic investigation of solvent-extracted R1 showed extensive deterioration of its normal morphology, including nucleocapsid disintegration and base plate separation. Routine phosphotungstate preparations demonstrated a particle with an oval head and a noncontractile tail. Altering the pH of the phosphotungstate negative stain from neutrality damage the viral particles. Uranyl formate-contrasted specimens displayed an elongated hexagonal nucleocapsid with a neck region; the cross-striated tail possessed a starlike base plate.

Isolation and characterization of nocardia-like variants of Mycobacterium smegmatis

Orange-red-pigmented (OR) colonies were isolated from cream-yellow-pigmented Mycobacterium smegmatis after exposure to either mycobacteriophage MC4 or ultraviolet light; these variant strains were designated OR4 and ORuv, respectively. Early subculture of OR-colonies did not show any segregation of parental-type cells. However, colonies resembling the parental strains, possibly representing a back mutant (REV-OR4), were occasionally found during subculture of established OR-colonies or upon treatment with N-nitrose-N'-nitro-N-methylguanidine. The OR-variants were characterized by their lytic response to nocardiophage, but not to mycobacteriophages, presence of alpha-branched, beta-hydroxylated fatty acids of the Nocardia-type, and a guanine plus cytosine value of deoxyribonucleic acid (DNA) between 62 and 64 mol%. They were more resistant to the lethal action of both ultraviolet light and mitomycin C treatment than the parental and back mutant strains. Although the OR-variants in this study possess characteristics common to the genus Nocardia or some of the 'rhodochrous' mycobacteria, evidence is presented that they form a new class of mycobacterial variants.

Evidence for host-dependent modification and restriction of bacteriophage DNA in Mycobacterium tuberculosis

Wild isolates of Mycobacterium tuberculosis may be divided into the three internationally recognized phage types on the basis of susceptibility to mycobacteriophages DS6A, BK1 and D34. Strains of type A are lysed at high efficiency by DS6A only; type B is lysed by BK1 grown on Mycobacterium smegmatis ATCC607 and DS6A, while type C is lysed additionally by D34 grown on atypical Mycobacterium F130. Propagation of D34 on a C-strain (D34-C) or BK1 on a B-strain (BK1-B) has no effect on viral host-range. D34-C has an efficiency of plating (e.o.p.) of 10(-5) on type B strains and 10(-7) on A strains. BK1-B plates on A strains at an e.o.p. of 10(-5). BK1 recovered from and repropagated on an A strain (BK1-A) has an e.o.p. of 1-0 on strains of all classes. D34-B has an e.o.p. of 1-0 on strains of type B and C, while D34-A plates with high efficiency on types B and C and displayed an e.o.p. of 10(-4) on type A. Repropagation of these viruses on the M. tuberculosis strains originally lysed by them results in the restoration of their previous host range. Variations in plating efficiency cannot be explained by differences in viral absorption alone. These findings suggest that the three phage types of human tubercle bacilli are related by a hierarchical pattern of DNA restriction and modification in which the C pattern is included in the B, and both patterns are included in A-modified DNA. Viruses such as DS6A which are equally virulent for strains of all classes are not susceptible to host dependent restriction.

Ultrastructure of L-phase variants isolated from a culture of Mycobacterium phlei

Relatively stable L-phase colonies were isolated from old cultures of a selected clone of Mycobacterium phlei. The colonies grew at 52 degrees C and were composed of rod-shaped, oval or spherical cells. Large amoeba-like cells were occasionally present. These were usually limited by a double-layered membrane and devoid of normal cell-wall components such as bacteriophage receptors. The large amoeba-like bodies sometimes showed both outer and inner double-layered membranes, especially in pseudopodium-like cellular extensions. An unusual feature of rod-shaped cells was retention of the original shape despite the loss of their cell walls. Two types of walled cells occurred during successive transfers of L colonies. One was the true revertant which had characteristics in common with the wild-type M. phlei, such as growth at 52 degrees C and ultrastructural organisation. The other, designated as the "atypical-cell-wall variant", was characterised by growth at 52 degrees C, thick cell walls, and disordered septation. Wild-type M. phlei, L variants, revertants and atypical-cell-wall variants released mycobacteriophage particles. These bacteriophages were almost identical in respect to morphology, host range, and neutralisation by antiserum. The results obtained suggest strongly that all types of cells examined were derived from M. phlei.

Differentiation of known strains of BCG from isolates of mycobacterium bovis and Mycobacterium tuberculosis by using mycobacteriophage 33D

The use of mycobacteriophage 33D to differentiate strains of BCG from isolates of Mycobacterium bovis was investigated. The procedure was found to be reproducible and, using the commercially available media described, can be recommended for use in mycobacterial reference laboratories.

Mycosides C: behavior as receptor site substance for mycobacteriophage D4

Interpretation of an earlier published infrared spectrum of Mycobacterium smegmatis lipids with receptor site activity for D4 phage led us to the inference that the active substance is very likely a mycoside C. This hypothesis was confirmed: the well-characterized mycosides C(s) and C(1217) elaborated by the heterologous strains M. scrofulaceum and Mycobacterium species 1217, respectively, are essentially indistinguishable from the smegmatis lipids in their behavior toward D4. Minute quantities adsorb and extensively inactivate the phage on appropriate incubations. In accord with derivative expectations, Mycobacterium species 1217 is a permissive host, attacked and lysed by D4. However, our current strains of M. butyricum, M. avium, and M. scrofulaceum, which reputedly produce various related mycosides C, are neither lysed by nor do they significantly adsorb the phage. Implications of these observations are discussed.

Anomalous induction of mycobacteriophages mediated by mitomycin C

Mitomycin C has been found to stimulate the production of long-tailed defective bacteriophages and poly tails in thick cell wall mycobacterial mutants.