Direct identification of Mycobacterium species in Bactec 7H12B medium by gas-liquid chromatography

Analysis of Cellular Fatty Acids inOrientia tsutsugamushias Taxonomic Markers

Six Orientia strains including 3 prototype strains such as Gilliam, Karp, and Kato, and 3 strains (Boryong, Pajoo, and Yongworl) isolated in Korea, were studied for the profiles of their cellular fatty acids. All tested strains contained octadecenoic acid C (18: 1) omega 9 c(57.3 +/- 3.5%), octadecanoic acid C (18: 0) (15.3 +/- 1.5%), and hexadecanoic acid C (16: 0) (12.7 +/- 1.7%) as major components; however, interestingly, eicosenoic acid C (20: 1) omega 9 c(2.6 +/- 0.6%) was found in all strains except the Yongworl strain. Furthermore none of the strains contained 3-hydroxy fatty acids. The ratios of total saturated fatty acid (SFA) to total unsaturated fatty acid (UFA) were within the range of 0.34 to 0.54. These results showed that the cellular fatty acid profile should provide more reliable information for the identification of these bacteria.

Polyketide synthases of bacterial symbionts in sponges--evolution-based applications in natural products research

Marine sponges are an unusually rich source of bioactive natural products with clinical potential. They also often harbor rich communities of symbiotic bacteria that have often been suspected as the true producers of sponge-derived compounds. To date, these bacteria can in most cases not be cultivated, but culture-independent methods, such as isolating and analyzing biosynthetic gene clusters using metagenomic strategies, have recently provided first insights into their chemical potential. This review summarizes recent work of our laboratory on the study of polyketide synthases (PKSs). These studies revealed two evolutionarily distinct, unusual PKS types that are commonly found in sponge metagenomes and were shown to be of bacterial origin. One, the sup PKS, dominates sponge metagenomic DNA libraries, occurs widespread in bacteriosponges and is to date exclusively known from such animals. Data suggest that it is a type of synthase that generates methyl-branched fatty acids, which are commonly present in sponges. The other PKS type, termed trans-acyltransferase (AT) PKS, is responsible for the biosynthesis of complex, bioactive polyketides, such as the onnamides, and also occurs in free-living bacteria. The diversity of PKS genes present in a single sponge metagenome can be enormous. However, the phylogenetic approaches outlined in this review can provide valuable insights into the PKS function and structures of polyketides and can assist in the targeted isolation of gene clusters.

Unique mechanism of action of the thiourea drug isoxyl on Mycobacterium tuberculosis

The thiourea isoxyl (thiocarlide; 4,4'-diisoamyloxydiphenylthiourea) is known to be an effective anti-tuberculosis drug, active against a range of multidrug-resistant strains of Mycobacterium tuberculosis and has been used clinically. Little was known of its mode of action. We now demonstrate that isoxyl results in a dose-dependent decrease in the synthesis of oleic and, consequently, tuberculostearic acid in M. tuberculosis with complete inhibition at 3 microg/ml. Synthesis of mycolic acid was also affected. The anti-bacterial effect of isoxyl was partially reversed by supplementing growth medium with oleic acid. The specificity of this inhibition pointed to a Delta9-stearoyl desaturase as the drug target. Development of a cell-free assay for Delta9-desaturase activity allowed direct demonstration of the inhibition of oleic acid synthesis by isoxyl. Interestingly, sterculic acid, a known inhibitor of Delta9-desaturases, emulated the effect of isoxyl on oleic acid synthesis but did not affect mycolic acid synthesis, demonstrating the lack of a relationship between the two effects of the drug. The three putative fatty acid desaturases in the M. tuberculosis genome, desA1, desA2, and desA3, were cloned and expressed in Mycobacterium bovis BCG. Cell-free assays and whole cell labeling demonstrated increased Delta9-desaturase activity and oleic acid synthesis only in the desA3-overexpressing strain and an increase in the minimal inhibitory concentration for isoxyl, indicating that DesA3 is the target of the drug. These results validate membrane-bound Delta9-desaturase, DesA3, as a new therapeutic target, and the thioureas as anti-tuberculosis drugs worthy of further development.

Gas-chromatographic lipid profiles in identification of currently known slowly growing environmental mycobacteria

Cellular fatty acid analysis by GLC is widely used in the species identification of mycobacteria. Combining mycolic acid cleavage products with shorter cellular fatty acids increases the informative value of the analysis. A key has been created to aid in the identification of all currently known slowly growing environmental species. In this scheme, the species are classified into six categories, each characterized by a combination of fatty markers shared by those species. Within each category, individual species may be distinguished by the presence or absence of specific marker substances, such as methyl-branched fatty acids or secondary alcohols. This study also describes earlier unpublished GLC profiles of 14 rare, slowly growing, environmental mycobacteria, Mycobacterium asiaticum, Mycobacterium botniense, Mycobacterium branderi, Mycobacterium conspicuum, Mycobacterium cookii, Mycobacterium doricum, Mycobacterium heckeshornense, Mycobacterium heidelbergense, Mycobacterium hiberniae, Mycobacterium kubicae, Mycobacterium lentiflavum, Mycobacterium scrofulaceum, Mycobacterium triplex and Mycobacterium tusciae. Though no single identification technique alone, even sequencing of an entire single gene such as 16S rRNA, can identify all mycobacterial species accurately, GLC has proven to be both reliable and reproducible in the identification of slowly growing mycobacteria. In cases of earlier unknown species, it generates useful information that allows their further classification and may lead to the description of novel species.

Identification of three strains of Mycobacterium species isolated from clinical samples using fatty acid methyl ester profiling

The cellular fatty acid profiles of 67 strains belonging to three different species of the genus Mycobacterium were determined by gas chromatography of the fatty acid methyl esters, using the MIDI Sherlock Microbial Identification System (MIS). The species M. tuberculosis, M. xenopi and M. avium complex were clearly distinguishable and could be identified based on the presence and concentrations of 12 fatty acids: 14:0, 15:0, 16:1 omega 7c, 16:1 omega 6c, 16:0, 17:0, 18:2 omega 6.9c, 18:1 omega 9c, 18:0, 10Me-18:0 tuberculostearic acid, alcohol and cyclopropane. Fatty acid analysis showed that there is great homogeneity within and heterogeneity between Mycobacterium species. Thus the MIS is an accurate, efficient and relatively rapid method for the identification of mycobacteria.

Testing of alkaline and enzymatic hydrolysis pretreatments for fat particles in slaughterhouse wastewater

Four pretreatments to hydrolyse and/or reduce the size of fat particles in slaughterhouse wastewater (SHW) were tested: sodium hydroxide and three lipases of plant, bacterial and animal (pancreatic) origin. Hydrolysing agents and SHW containing between 2.5 and 3 g/l of fat particles were mixed at room temperature for 4 h. Additions of 5-400 meq NaOH/l did not increase soluble COD (SCOD) in SHW, but the average particle size was reduced to 73% +/- 7% of the initial average particle size (D(in)) at NaOH concentrations ranging from 150 to 300 meq/l. Pretreatment with pancreatic lipase PL-250 reduced the average particle size to a maximum of 60% +/- 3% of D(in). As D(in) was decreased from 359 to 68 microns, the enzyme concentration required to obtain the maximum particle size reduction increased from 200 to 1000 mg/l. A 4-h pretreatment with PL-250 also increased the free long-chain fatty acid (LCFA) concentration to a maximum of 15.5 mg/l, indicating some solubilization of the pork fat particles in SHW. SCOD was not significantly increased by the pretreatment, but SCOD was not found to be a good indicator of enzymatic lipolysis because of enzyme adsorption on the fat particle surface. Pancreatic lipase appeared more efficient with beef fat than pork fat, possibly because beef fat contains less polyunsaturated fatty acids than pork fat. The bacterial lipase LG-1000 was also efficient in reducing average fat particle size, but high doses (> 1000 mg/l) were required to obtain a significant reduction after 4 h of pretreatment. SCOD was not increased by pretreatment with LG-1000. No particle size reduction or changes in SCOD were noted after 4 h of pretreatment with the plant lipase EcoSystem Plus. It was concluded that PL-250 was the best pretreatment to hydrolyse fat particles in SHW. However, its impact on the efficiency of a downstream anaerobic digestion process remains to be tested.

Characterization of novel methyl-branched chain fatty acids from a halophilic Bacillus species

The 4-methylated fatty acids 4,9-dimethyldecanoic, 4,11-dimethyldodecanoic, 4,10-dimethyldodecanoic, and 4,13-dimethyltetradecanoic acid as well as the 2-methylated fatty acids 2,13-dimethyltetradecanoic and 2,12-dimethyltetradecanoic acid were identified for the first time in nature in the halophilic bacterium Bacillus sp. isolated from the salt pans of Burgas in Bulgaria. The principal fatty acids in this bacterium were a series of iso-anteiso fatty acids with chain lengths between C11 and C19, but an interesting series of linear alkylbenzene fatty acids with chain lengths between C10 and C14, such as 12-phenyldodecanoic acid, were also identified. The novel 4-methylated fatty acids were characterized using a combination of GC-MS and chemical transformations such as N-acylpyrrolidide derivatization. The 2-methylated fatty acids were also identified by GC-MS and gas chromatographic coelution with synthetic samples. The novel methyl-branched fatty acids probably originated from the selective incorporation of methylmalonyl-CoA by one of the fatty acid-synthesizing enzymes of the bacterium.

Use of gas chromatographic fatty acid and mycolic acid cleavage product determination to differentiate among Mycobacterium genavense, Mycobacterium fortuitum, Mycobacterium simiae, and Mycobacterium tuberculosis

Three Mycobacterium genavense strains and three American Type Culture Collection reference strains each of Mycobacterium fortuitum, Mycobacterium simiae, and Mycobacterium tuberculosis were subcultured onto Mycobacteria 7H11 agar (Difco Laboratories, Detroit, Mich.) supplemented with mycobactin J (Allied Laboratories, Fayette, Mo.). After 4 weeks of incubation at 37 degrees C in 10% CO2, the cultures were analyzed by gas-liquid chromatography (GLC) for their fatty acids and mycolic acid cleavage products. M. fortuitum was clearly differentiated from M. genavense by the presence of the specific marker 2-methyloctadecenoic acid in M. fortuitum and by the ratio of tetracosanoic acid to hexacosanoic acid. This ratio was <1 for M. genavense and >3 for M. fortuitum. M. fortuitum also contained docosanoic acid, which was not detected in M. genavense. M. genavense, M. simiae, and M. tuberculosis, which have similar GLC profiles, were also differentiated from each other by the presence of either cis-10-hexadecenoic acid or cis-11-hexadecenoic acid and by tetradecanoic acid content.