Characterization of clostridia by gas chromatography. I. Differentiation of species by cellular fatty acids

Detection of Species-Specific Lipids by Routine MALDI TOF Mass Spectrometry to Unlock the Challenges of Microbial Identification and Antimicrobial Susceptibility Testing

MALDI-TOF mass spectrometry has revolutionized clinical microbiology diagnostics by delivering accurate, fast, and reliable identification of microorganisms. It is conventionally based on the detection of intracellular molecules, mainly ribosomal proteins, for identification at the species-level and/or genus-level. Nevertheless, for some microorganisms (e.g., for mycobacteria) extensive protocols are necessary in order to extract intracellular proteins, and in some cases a protein-based approach cannot provide sufficient evidence to accurately identify the microorganisms within the same genus (e.g., Shigella sp. vs E. coli and the species of the M. tuberculosis complex). Consequently lipids, along with proteins are also molecules of interest. Lipids are ubiquitous, but their structural diversity delivers complementary information to the conventional protein-based clinical microbiology matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) based approaches currently used. Lipid modifications, such as the ones found on lipid A related to polymyxin resistance in Gram-negative pathogens (e.g., phosphoethanolamine and aminoarabinose), not only play a role in the detection of microorganisms by routine MALDI-TOF mass spectrometry but can also be used as a read-out of drug susceptibility. In this review, we will demonstrate that in combination with proteins, lipids are a game-changer in both the rapid detection of pathogens and the determination of their drug susceptibility using routine MALDI-TOF mass spectrometry systems.

Role of fatty acids in Bacillus environmental adaptation

The large bacterial genus Bacillus is widely distributed in the environment and is able to colonize highly diverse niches. Some Bacillus species harbor pathogenic characteristics. The fatty acid (FA) composition is among the essential criteria used to define Bacillus species. Some elements of the FA pattern composition are common to Bacillus species, whereas others are specific and can be categorized in relation to the ecological niches of the species. Bacillus species are able to modify their FA patterns to adapt to a wide range of environmental changes, including changes in the growth medium, temperature, food processing conditions, and pH. Like many other Gram-positive bacteria, Bacillus strains display a well-defined FA synthesis II system that is equilibrated with a FA degradation pathway and regulated to efficiently respond to the needs of the cell. Like endogenous FAs, exogenous FAs may positively or negatively affect the survival of Bacillus vegetative cells and the spore germination ability in a given environment. Some of these exogenous FAs may provide a powerful strategy for preserving food against contamination by the Bacillus pathogenic strains responsible for foodborne illness.

Transcriptomic analysis of (group I) Clostridium botulinum ATCC 3502 cold shock response

Profound understanding of the mechanisms foodborne pathogenic bacteria utilize in adaptation to the environmental stress they encounter during food processing and storage is of paramount importance in design of control measures. Chill temperature is a central control measure applied in minimally processed foods; however, data on the mechanisms the foodborne pathogen Clostridium botulinum activates upon cold stress are scarce. Transcriptomic analysis on the C. botulinum ATCC 3502 strain upon temperature downshift from 37°C to 15°C was performed to identify the cold-responsive gene set of this organism. Significant up- or down-regulation of 16 and 11 genes, respectively, was observed 1 h after the cold shock. At 5 h after the temperature downshift, 199 and 210 genes were up- or down-regulated, respectively. Thus, the relatively small gene set affected initially indicated a targeted acute response to cold shock, whereas extensive metabolic remodeling appeared to take place after prolonged exposure to cold. Genes related to fatty acid biosynthesis, oxidative stress response, and iron uptake and storage were induced, in addition to mechanisms previously characterized as cold-tolerance related in bacteria. Furthermore, several uncharacterized DNA-binding transcriptional regulator-encoding genes were induced, suggesting involvement of novel regulatory mechanisms in the cold shock response of C. botulinum. The role of such regulators, CBO0477 and CBO0558A, in cold tolerance of C. botulinum ATCC 3502 was demonstrated by deteriorated growth of related mutants at 17°C.

Phylogenetic and experimental characterization of an acyl-ACP thioesterase family reveals significant diversity in enzymatic specificity and activity

Background

Acyl-acyl carrier protein thioesterases (acyl-ACP TEs) catalyze the hydrolysis of the thioester bond that links the acyl chain to the sulfhydryl group of the phosphopantetheine prosthetic group of ACP. This reaction terminates acyl chain elongation of fatty acid biosynthesis, and in plant seeds it is the biochemical determinant of the fatty acid compositions of storage lipids.

Results

To explore acyl-ACP TE diversity and to identify novel acyl ACP-TEs, 31 acyl-ACP TEs from wide-ranging phylogenetic sources were characterized to ascertain their in vivo activities and substrate specificities. These acyl-ACP TEs were chosen by two different approaches: 1) 24 TEs were selected from public databases on the basis of phylogenetic analysis and fatty acid profile knowledge of their source organisms; and 2) seven TEs were molecularly cloned from oil palm (Elaeis guineensis), coconut (Cocos nucifera) and Cuphea viscosissima, organisms that produce medium-chain and short-chain fatty acids in their seeds. The in vivo substrate specificities of the acyl-ACP TEs were determined in E. coli. Based on their specificities, these enzymes were clustered into three classes: 1) Class I acyl-ACP TEs act primarily on 14- and 16-carbon acyl-ACP substrates; 2) Class II acyl-ACP TEs have broad substrate specificities, with major activities toward 8- and 14-carbon acyl-ACP substrates; and 3) Class III acyl-ACP TEs act predominantly on 8-carbon acyl-ACPs. Several novel acyl-ACP TEs act on short-chain and unsaturated acyl-ACP or 3-ketoacyl-ACP substrates, indicating the diversity of enzymatic specificity in this enzyme family.

Conclusion

These acyl-ACP TEs can potentially be used to diversify the fatty acid biosynthesis pathway to produce novel fatty acids.

Applications of cellular fatty acid analysis

More than ever, new technology is having an impact on the tools of clinical microbiologists. The analysis of cellular fatty acids by gas-liquid chromatography (GLC) has become markedly more practical with the advent of the fused-silica capillary column, computer-controlled chromatography and data analysis, simplified sample preparation, and a commercially available GLC system dedicated to microbiological applications. Experience with applications in diagnostic microbiology ranges from substantial success in work with mycobacteria, legionellae, and nonfermentative gram-negative bacilli to minimal involvement with fungi and other nonbacterial agents. GLC is a good alternative to other means for the identification of mycobacteria or legionellae because it is rapid, specific, and independent of other specialized testing, e.g., DNA hybridization. Nonfermenters show features in their cellular fatty acid content that are useful in identifying species and, in some cases, subspecies. Less frequently encountered nonfermenters, including those belonging to unclassified groups, can ideally be characterized by GLC. Information is just beginning to materialize on the usefulness of cellular fatty acids for the identification of gram-positive bacteria and anaerobes, despite the traditional role of GLC in detecting metabolic products as an aid to identification of anaerobes. When species identification of coagulase-negative staphylococci is called for, GLC may offer an alternative to biochemical testing. Methods for direct analysis of clinical material have been developed, but in practical and economic terms they are not yet ready for use in the clinical laboratory. Direct analysis holds promise for detecting markers of infection due to an uncultivable agent or in clinical specimens that presently require cultures and prolonged incubation to yield an etiologic agent.

Identification of Clostridium botulinum, Clostridium argentinense, and related organisms by cellular fatty acid analysis

On the basis of 686 analyses of 285 strains of Clostridium botulinum, Clostridium argentinense (formerly C. botulinum type G), and phenotypically related organisms, 14 cellular fatty acid (CFA) groups of toxic organisms and 6 CFA groups of nontoxic organisms were delineated. The CFA groups of toxic strains included two of type A, three of proteolytic strains of type B, two of proteolytic strains of type F, one each of nonproteolytic strains of types B, E, and F, and one each of types C alpha, C beta, and D and C. argentinense. The groups of phenotypically similar nontoxic strains included Clostridium sporogenes, Clostridium putrificum, nontoxic strains with phenotypic characteristics similar to those of nonproteolytic strains of C. botulinum types B, E, and F (BEF-like), two groups of nontoxigenic organisms with phenotypic characteristics similar to those of C. botulinum types C and D and Clostridium novyi (CDN-like), and Clostridium subterminale, which has phenotypic characteristics similar to those of C. argentinense. Within the toxin types, 89 to 100% of the strains were correctly identified by CFA analysis, and 74 to 100% of the analyses were correct. Of 36 strains of C. sporogenes, 30 (83%) were correctly identified; 17% of the strains of C. sporogenes were incorrectly identified as C. botulinum type A or B. All analyses of C. putrificum and C. subterminale were correctly identified. There was no significant level of similarity between strains of C. botulinum and phenotypically similar organisms and 85 other species of clostridia or 407 other taxa of gram-positive and gram-negative bacteria. Additionally, the one strain each of Clostridium baratii and Clostridium butyricum previously reported to produce C. botulinum toxin could be differentiated from C.botulinum types as well as from strains of C. baratii and C. butyricum that did not produce neurotoxin.

Mechanism of resistance to benzalkonium chloride by Pseudomonas aeruginosa

The mechanisms of resistance of Pseudomonas aeruginosa to benzalkonium chloride (BC) were studied. The effluence of cell components was observed in susceptible P. aeruginosa by electron microscopy, but resistant P. aeruginosa seemed to be undamaged. No marked changes in cell surface potential between Escherichia coli NIHJC-2 and a spheroplast strain were found. The contents of phospholipids (PL) and fatty and neutral lipids (FNL) in the cell walls of resistant P. aeruginosa were higher than those in the cell walls of susceptible P. aeruginosa. The amounts of BC adsorbed to PL and FNL of cell walls of BC-resistant P. aeruginosa were lower than those for BC-susceptible P. aeruginosa. Fifteen species of cellular fatty acids were identified by capillary gas chromatography and gas chromatography-mass spectrometry. The ability of BC to permeate the cell wall was reduced because of the increase in cellular fatty acids. These results suggested that the resistance of P. aeruginosa to BC is mainly a result of increased in the contents of PL and FNL. In resistant P. aeruginosa, the decrease in the amount of BC adsorbed is likely to be the result of increases in the contents of PL and FNL.

Lipid composition and sensitivity of Prototheca wickerhamii to membrane-active antimicrobial agents

The lipid composition of Prototheca wickerhamii ATCC 16529 is presented and discussed in relation to the unique susceptibility of the organism to drugs of three membrane-active antimicrobial classes: the polyenes, the polymyxins, and the imidazoles. The presence of ergosterol in the neutral lipid fraction of the membrane is likely responsible for the exquisite susceptibility to amphotericin B. The presence of a large quantity of free fatty acids in the membrane appears responsible for imidazole susceptibility. The membrane determinants of polymyxin B susceptibility are less well defined.

Fatty acid fingerprints of Streptococcus mutans NCTC 10832 grown at various temperatures

Fatty acid fingerprints were determined gas chromatographically for Strepcococcus mutans NCTC 1082 which had been grown in batch brain heart infusion at a series of nine temperatures ranging from 29.0 to 40.0 degrees C. The major acids at all temperatures were n-palmitic and octadecenoic acids. Other acids detected at all temperatures included n-myristic, palmitoleic, n-stearic, and eicosenoic acids. An increase in temperature resulted in a decrease in the proportion of unsaturated to saturated fatty acids, indicating the importance of accurate temperature control in such gas-liquid chromatographic, chemotaxonomic studies.

Cellular fatty acids and metabolic products of Pseudomonas species obtained from clinical specimens

The cellular fatty acid composition of 112 reference strains and clinical isolates of Pseudomonas species was determined by gas-liquid chromatography (GLC). The presence and relative amounts of cyclopropane, hydroxy, and branched-chain fatty acids were distinguishing features of these strains. Determination of short-chain fatty acids extracted from spent growth media provided an additional means for identifying some strains. Our results show that clinical isolates of pseudomonads can be divided into eight distinct GLC groups. The procedures were especially useful for distinguishing glucose-nonoxidizing pseudomonads, which are difficult to identify by conventional criteria. Since the GLC procedures are simple, rapid, and highly reproducible, they are useful in diagnostic laboratories that process large numbers of cultures. Coupled with selected conventional tests, the analysis of short-chain and cellular fatty acids can be very useful for rapid screening of clinical isolates of Pseudomonas species.

Rapid diagnosis of anaerobic infections by direct gas-liquid chromatography of clinical speciments

Current methods to isolate and identify anaerobic bacteria are laborious and time consuming. It was postulated that the short-chain fatty acids (SCFA) produced by these organisms might serve as microbial markers in clinical material. 98 specimens of pus or serous fluid were analyzed by gas-liquid chromatography, and findings were compared with culture results. Good correlations were found for the recovery of anaerobic Gram-negative bacilli and the presence of isobutyric, butyric, and succinic acids. 19 of 20 specimens with significant amounts of these acids (greater than 0.01 mumol/ml) yielded bacteroides or fusobacteria. Culture of the single "false-positive" specimen failed to grow anaerobic Gram-negative bacilli, although clinical data and Gram-stain suggested their presence. 77 of 78 specimens which has insignificant concentrations of the marker acids failed to yield anaerobic, Gram-negative bacilli in culture. The single "false-negative" specimen yielded Bacteroides pneumosintes, an organism which does not ferment carbohydrates. It is concluded that direct gas-liquid chromatographic analysis of clinical specimens provides a rapid presumptive test for the presence of anaerobic, Gram-negative bacilli.

Phospholipids and fatty acids of Neisseria gonorrhoeae

The phospholipids and fatty acids of two strains of Neisseria gonorrhoeae of different penicillin susceptibilities were examined. The phospholipids, which comprise about 8% of the dry weight of the cells, consisted of phosphatidylethanolamine (70%) and phosphatidylglycerol (20%); small amounts of phosphatidylcholine and traces of cardiolipin were also present. Growing and stationary-phase cells were similar in content and composition of phospholipids except for phosphatidylcholine, which increased two- to fivefold in the stationary-phase cells. The fatty acids of the phospholipids were characterized by two major acids, palmitic and a C16:1, with myristic and a C18:1 acid present in smaller amounts. The fatty acids present in purified phospholipid fractions varied considerably in relative proportions from fraction to fraction. No significant difference in the composition of phospholipids from the two strains was evident. Large amounts of beta-hydroxy lauric acid were detected only after saponification of the organisms. Differences in the lipid composition between the gonococcus and other gram-negative bacteria are discussed.

Cultural and biochemical characteristics and fatty acid composition of Pseudomonas diminuta and Pseudomonas vesiculare

The cultural characteristics, biochemical activity, and cellular fatty acid composition of Pseudomonas diminuta and Pseudomonas vesiculare provided means for differentiation of these closely related species. Broth cultures of P. diminuta showed turbid growth and a distinct surface pellicle after 24 h at 35 C. P. vesiculare had no pellicle, and only light, diffuse growth was observed. All strains of P. vesiculare oxidized maltose and hydrolyzed esculin to varying degrees; P. diminuta was negative in these tests. The cellular fatty acids of these two species were similar, except that P. diminuta possessed a C19 cyclopropane acid which was not detected in P. vesiculare.

Occurrence of branched-cahin hydroxy fatty acids in Pseudomonas maltophilia

Three branched-chain hydroxy acids not previously reported in other bacteria were found in extracts from saponified whole cells of Pseudomonas maltophilia. On the basis of evidence from mass spectrometry, infrared spectroscopy, and gas chromatographic procedures, they were identified as 2-hydroxy-9-methyldecanoic acid, 3-hydroxy-9-methyldecanoic acid, and 3-hydroxy-11-methyldodecanoic acid. These acids appeared to be tightly bound to other cellular components since they were not extracted from lyophilized cells with a chloroform-methanol (3:1) mixture.

Cellular fatty acid composition of selected Pseudomonas species

The cellular fatty acid composition of 10 reference strains representing eight species of Pseudomonas was determined by gas-liquid chromatography. A variety of acids were detected in these organisms, including branched and straight-chained acids, cyclopropane, and hydroxy acids. Comparison of the presence and relative amounts of these acids among strains was useful for distinguishing various Pseudomonas species.

Lipid composition of growing and starving cells of Arthrobacter crystallopoietes

The lipid composition of growing and starving cells of Arthrobacter crystallopoietes was compared. Although the lipid composition of the two cell types was similar, the amount of total lipids recovered from the starving cells was 30.4% less than that recovered from the growing cells. The loss of lipids, as compared to the loss of total cell mass during starvation, was (i) proportional to the loss of the cell mass (phosphatidylinositol, phosphatidylglycerol-2, and cardiolipin), (ii) greater than the loss in cell mass (neutral lipids, "glycophospholipids," and phosphatidic acid), or (iii) less than the loss in cell mass (coenzyme Q, glycolipids, and phosphatidylglycerol-1).

Fatty acids of Mycobacterium kansasii

The cellular fatty acids of 35 strains of Mycobacterium kansasii isolated from clinical material were analyzed to establish properties by which we could identify and characterize these acid-fast microorganisms. The fatty acids were extracted from cells grown in liquid synthetic media, and they were analyzed as methyl esters by gas-liquid chromatography. The fatty acid profiles of all strains were similar. They differed from fatty acid profiles of other mycobacteria by their content of a saturated fatty acid with a methyl group at C2.

Analysis of Clostridium botulinum toxigenic types A, B, and E for fatty and carbohydrate content

Lyophilized, 48-hr log-phase vegetative cells were extracted with chloroform-methanol (2:1, v/v) and ethanol-ether (3:1, v/v) and then saponified with methanolic KOH. Gas-liquid chromatography of the methyl esters of extractable fatty acids revealed distinctive "pattern profiles" of Clostridium botulinum toxigenic types "A," "B," and "E." C. perfringens type "A" and Escherichia coli strain "B" were also studied in a similar manner and were found to give pattern profiles which were distinct even from those obtained for the C. botulinum microorganisms. Amino sugar content of the five microorganisms was determined by using a Beckman amino acid analyzer. The molar ratio of glucosamine to that of galactosamine was found to be of further assistance in distinguishing the individual microorganisms.

Pyrolysis-gas-liquid chromatography of fungi: differentiation of species and strains of several members of the Aspergillus flavus group

Four fungi of the Aspergillus flavus group were differentiated to the species level and strain level by pyrolysis-gas-liquid chromotography. Comparisons of pyrochromatograms revealed more similarities than dissimilarities among both species and strains in the pyrolytic elution patterns. Quantitative analysis was made by comparing the number of peaks in which two strains or reference species agreed or disagreed, the degree of superimposability between the pyrolytic elution patterns of strains and reference species, and the presence or absence of peaks for strain pairs within each species. The accuracy and precision of these techniques suggest that pyrolysis-gas-liquid chromatography may have wide application in the detection, enumeration, and identification of fungi by nonmycologically trained personnel.

Cellular fatty acids of pathogenic Neisseria

The cellular fatty acid composition of 20 isolates of Neisseria gonorrhoeae and 21 isolates of N. meningitidis was examined by gas-liquid chromatography. Each isolate of the two species possessed similar fatty acid profiles which were characterized by five major acids, accounting for 80 to 85% of the total. The three most abundant acids in each species were palmitic, palmitoleic, and beta-hydroxylauric acids; lauric and myristic acids were the next most abundant. The presence of large amounts of beta-hydroxylauric acid (20% or greater) and the relative concentrations of the other four major acids appear to be useful markers for distinguishing N. gonorrhoeae and N. meningitidis fatty acids from those of other bacteria.

Characterization of clostridia by gas chromatography differentiation of species by trimethylsilyl derivatives of whole-cell hydrolysates

Trimethylsilyl (TMS) derivatives prepared from whole-cell hydrolysates of 36 strains, representing 10 species of Clostridium were examined by gas-liquid chromatography (GLC). The TMS profile of each species contained a group of peaks which characterized the species. Variation among strains within a species was much lower than variation between species. Some of the closely related clostridia could be differentiated by comparing their TMS profiles. Strains of Clostridium botulinum were distinguished from C. sporogenes on the basis of the ratio of two GLC peaks which corresponded to arabinose and glucose. A peak with a retention time identical to that of mannose was present in all C. bifermentans strains but was absent in those of C. sordellii.

Differentiation of two groups of Corynebacterium acnes

One hundred and forty-three strains of Corynebacterium acnes, isolated from human skin and acne lesions, were compared with three strains of Propionibacterium acnes from the American Type Culture Collection. The 146 organisms could be separated into two groups. Members of the larger group (129 strains) hydrolyzed gelatin and usually produced indole, Gel-In(+), but were unable to ferment trehalose, maltose, or sucrose, TMS(-). The deoxyribonucleic acid from selected strains of this group had an average guanosine + cytosine (GC) content of 60.5%. The members of the smaller group (17) were Gel-In(-), TMS(+), and the deoxyribonucleic acid had an average GC content of 63.9%. Studies with absorbed and unabsorbed antisera to the smaller group showed that although there were antigens shared by the two groups, it was possible to distinguish them serologically. Members of each group produced propionic acid. The principal fatty acid component of members of each group was iso-C(15) fatty acid. Seventy per cent of the Gel-In(+) strains were lysed by phage 174, whereas only one of 15 Gel-In(-) strains was lysed. Pending further information on the genetics of the two groups, those Gel-In(-), TMS(+) strains are tentatively designated C. acnes, group II.

Demonstration of treponeme-like forms in cases of treated and untreated late syphilis and of treated early syphilis

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Production of hydrocinnamic acid by clostridia

Hydrocinnamic acid was found in acid extracts of spent growth medium from cultures of Clostridium sporogenes. The acid was identified by mass spectrometry and its identity was confirmed by gas chromatography. The acid was produced in relatively large amounts (2 to 3 mumoles/ml of medium) by C. sporogenes, toxigenic types A, B, D, and F of C. botulinum, and some strains of C. bifermentans. Other strains of C. bifermentans and strains of C. sordellii and C. caproicum produced only small amounts (0.1 to 0.4 mumoles/ml) of the acid. The acid was not detected in spent medium from toxigenic types C and E of C. botulinum or from 25 other strains representing eight Clostridium species. Resting cell suspensions exposed to l-phenylalanine produced hydrocinnamic and cinnamic acid; the latter compound probably functions as an intermediate in the metabolism of l-phenylalanine.

Volatile and cellular fatty acids of Haemophilus vaginalis

The major volatile acid produced by Haemophilus vaginalis was acetic acid. The absence of propionate, butyrate, and cellular branched-chain fatty acids indicates that H. vaginalis is not related to Propionibacterium or Butyribacterium.

Cultural characteristics and fatty acid composition of propionibacteria

The cultural characteristics and cellular fatty acid composition of 40 strains representing 7 species of Propionibacterium and of 9 cultures of anaerobic corynebacteria were studied. The cultures were characterized by means of 23 separate cultural and biochemical tests. Cultures of the two genera differed consistently in only two reactions; the propionibacteria did not produce indole or liquefy gelatin, whereas the anaerobic corynebacteria were consistently positive with these tests. The fatty acids were extracted from whole cells and examined as methyl esters by gas-liquid chromatography. The most abundant acid in the seven Propionibacterium species was a C(15)-saturated branched-chain acid which was present in both the iso-and anteiso-form. Based on a comparison of the relative abundance of these isomers (i-C(15) and a-C(15)), the species were separated into two groups. P. freudenreichii and P. shermanii (group one) were similar and contained the a-C(15) isomer as the predominant acid. The i-C(15) isomer was the most abundant acid in the second group (P. arabinosum, P. jensenii, P. pentosaceum, P. thoenii, and P. zeae). The fatty acid profiles of the anaerobic corynebacteria were somewhat similar to those of the second group of propionibacteria, but were distinct from the profiles of P. freudenreichii and P. shermanii. The addition of branched-chain amino acids (l-leucine and l-isoleucine) to the growth medium increased the synthesis of the specific fatty acid(s) structurally related to the added amino acid.

Characterization of bacteria by gas chromatography: comparison of trimethylsilyl derivatives of whole-cell hydrolysates

A method for the formation of the trimethylsilyl (TMS) derivatives of the whole-cell hydrolysate of bacteria was developed. The TMS derivatives were examined by gas-liquid chromatography. TMS profiles of various bacteria at the genus and species level were compared. Differences in TMS profiles of Listeria, Neisseria, and Clostridium were significant as were differences between the TMS profiles of C. perfringens and C. sporogenes. Two types of C. perfringens, two serotypes of L. monocytogenes, and one culture of C. sporogenes and N. meningitidis were studied. The possible application of TMS profiles as an aid in differentiating closely related organisms which are troublesome to separate by conventional means is discussed.

Cellular fatty acid composition and identification of rumen bacteria

The fatty acid compositions of 21 pure cultures of rumen bacteria, representing 12 genera and 14 species, were compared as methyl esters. Each organism possessed a consistent and reproducible fatty acid profile. Overlapping similarities and differences in composition did not allow differentiation between families or genera. Although species differentiation was possible, fatty acid composition appeared to be only an aid in the identification of bacteria.

Fatty acid composition of Neisseria species as determined by gas chromatography

Duplicate cultures of 53 strains representing 9 species of Neisseria were analyzed by gas-liquid chromatography for cellular fatty acids. N. sicca, N. mucosa, N. flava, N. flavescens, N. perflava, N. subflava, and the several serotypes of N. meningitidis examined were found to comprise a fairly homogeneous group on the basis of the percentages of individual fatty acids present. Lactose-fermenting Neisseria also were in this group. N. catarrhalis, however, contained decanoic acid in addition to the acids occurring in the other species. Moreover, the 18 C-saturated and monoenoic acids together constituted 36% of the total fatty acid composition for N. catarrhalis, while the comparable mean value for the other species was less than 13%.

Gas chromatography for detection of viral infections

Gas chromatograms of sertim extracts of dogs inoculated with canine infectious hepatitis virus showed two metabolites not observed in uninoculated animals. Chromatograms of extracts of tissue cultures of dog kidney, inoculated with viruses causing canine hepatitis, herpes, and distemper, and a parainfluenza virus similar to simian virus-5, each showed two or more different metabolites. Two of the distinguishing products from cultures inoculated with hepatitis virus were chromatographically indistinguishable from those found in serums of the animals.

Rapid and sensitive detection of bacteria by gas chromatography

A gas chromatograph fitted with electron capture and flame ionization detectors was employed for the rapid detection of bacteria by analysis for their metabolic products. The presence of Proteus vulgaris, Streptococcus faecalis, S. liquefaciens, Escherichia coli B, Bacillus cereus, and B. popilliae was detected in 2 to 4 hr in media inoculated with less than 10(4) cells per ml, whereas a 7- to 12-hr growth period was required for the detection of products formed in cultures of Serratia marcescens, Aerobacter aerogenes, E. coli K-12, Staphylococcus aureus, and Salmonella typhimurium. Metabolites elaborated by the equivalent of less than a single cell of B. cereus, S. faecalis, P. vulgaris, or E. coli B were sensed by the electron capture detector. The flame ionization detector was generally not as sensitive. Volatile metabolites were identified, and their concentrations were determined.

Cultural characteristics and fatty acid composition of Corynebacterium acnes

A detailed study of the cultural characteristics and cellular fatty acid composition of 27 isolates of Corynebacterium acnes was performed to establish the properties by which this organism may be identified and characterized. The fatty acids were extracted directly from whole cells and examined as methyl esters by gas-liquid chromatography. Each strain possessed a similar fatty acid profile which was characterized by a large percentage of C15 branched-chain acid. Uniformity in certain biochemical reactions and cultural characteristics was also observed. All strains were catalase-positive, nonmotile, and urease-negative, reduced nitrate, liquefied gelatin, failed to hydrolyze esculin and starch, and gave a positive methyl red test. Glucose, fructose, and glycerol were fermented, but not lactose, salicin, sucrose, maltose, xylose, or arabinose. Production of hydrogen sulfide and indole, fermentation of mannitol, and hemolytic activity were variable characteristics. Two species of the genus Propionibacterium were also tested and found to be similar to C. acnes both in cultural characteristics and fatty acid composition. The results strengthen previous suggestions that C. acnes should be classified in the genus Propionibacterium.