Bacteria branched fatty acids

A number of amide- and ester-linked fatty acids and (/ )-3-hydroxy acids are components of the lipid A part in the LPS from Gram-negative bacteria. The acids have been tabulatedand the chemistry of lipid A summarized. The most common acids in lipid A from Enterobacteriaceae are the saturated 12 0,14 0, and 16 0, and the (/ )-3-hydroxy-14 0, The last is linked to N-2 and 0-3 of the 2-amino-2-deoxy-D-glucopyranosyl residues, and the others are ester-linked to the hydroxy acid, as in the lipid A (44) of Salmonella minnesota. Other linear and branched fatty acids, unsaturated acids, S)-2- and (/ )-3-hydroxy acids, and 3-oxotetradecanoic acid are components of lipid A from certain different species. In the lipid A from Rhizobium trifolii, 2,7-dihydroxyoctanoic acid is linked as amide to a 2-amino-2-deoxy-D-gl ucopy ranosy 1 residue. ... 

Bacteria usually lack polyunsaturated fatty acids but often contain branched fatty acids, cyclopropane-containing acids, hydroxy fatty acids, and unesterified fatty acids. Mycobacteria, including the human pathogen Mycobacterium tuberculosis, contain mycolic acids. In these compounds the complex grouping R contains a variety of functional groups including -OH, -OCH3,... 

Bacteria 2. See also Specific genus and species acetic acid 8 aerobes 10 anaerobic 8 autotrophic 8 binding to cells 186 branched fatty acids of 381 chemoheterotrophic 7,8 chemolithotrophic 7 classification of 6-8 coats 431 composition of 31 electron micrograph of 4 flagella 6... 

Fatty acids containing one or more cyclopropane rings are present in many bacteria (p. 381).124 125 The extra carbon of the cyclopropane ring is added from S-adenosylmethionine (AdoMet) at the site of a cis double bond in a fatty acyl group of a phosphatidyle-thanolamine molecule in a membrane (Eq. 21-4).126/1263 The same type of intermediate carbocation can yield either a cyclopropane fatty acid (Eq. 21-4, step a) or a methenyl fatty acid (Eq. 21-4, step b). The latter can be reduced to a branched fatty acid. This is an alternative way of introducing methyl branches that is used by some bacteria.127... 

Branched-chain fatty acids (BrFAs) (iso- and anteiso) are believed to be primarily derived from sulfate-reducing bacteria (Perry et al., 1979 Cranwell, 1982 Canuel et al., 1995 table 9.5). However, it should be noted that BrFAs are not present in all sulfate-reducing bacteria or other heterotrophic bacteria (Kaneda, 1991 Kohring et al., 1994). The iso- and antesio- designation represents a branched fatty acid with the methyl group at the a>-l position and the methyl group at the a>-2 position, respectively. The odd number (C45, C17, branched and normal) are believed to be derived from phospholipids, components of bacterial cell membranes (Kaneda, 1991). Even-numbered iso-branched fatty acids (e.g., C12—Cig) are also found in algal sources (Schnitzer and Khan, 1972). 

Branched fatty acids iso- and anteiso fatty acids believed to be primarily derived from sulfate-reducing bacteria the iso- and antesio designation represents a branched fatty acid with the methyl group at the w-1 position and the methyl group at the co-2 position, respectively. 

Several fatty acids, specifically 15 0, 17 0 and all branched fatty acids, are produced primarily by both aerobic and anaerobic bacteria [55-57] and the sum of those fatty acids has been used to estimate bacterial contributions [58-61]. A comparison of bacterial markers in plankton, sediment trap and sediment samples showed the lowest values, with little variation, in plankton samples (Fig. 3 b), and the greatest bacterial levels in sediments. The sediment traps, containing partially degraded material, had bacterial marker levels intermediate between the other two sample types, and levels of bacterial markers increased with increasing period of deployment. However, there are conflicting theories concerning the usefulness of these markers and, for that reason, bacterial markers should only be employed with caution. For instance, in a recent paper, Harvey and Macko [57] did not find a correlation between total fatty acids attributed to bacteria and bacterial carbon, and they suggest that bacterial fatty acids only be used as qualitative tools to estimate bacterial contributions. Wakeham [62] also points out that fatty acids of common oceanic bacteria may not be compositionally different from planktonic fatty acids so that bacterial... 

Fatty acids in the 12-20 carbon chain-length range account for the majority of bacterial fatty acids. These are usually saturated or monounsaturated polyunsaturated fatty acids only occur in a few species, such as the gliding bacteria which accumulate large amounts of arachidonate (Fautz et al., 1979) or cyanobacteria which contain linoleate and linolenate. Reports of polyunsaturated fatty acids in bacteria should be treated with scepticism because of the ease with which bacteria can take up growth constituents which can include polyunsaturates. Besides the ubiquitous even-chain saturated and unsaturated fatty acids bacteria characteristically contain odd-chain and branched fatty acids as well as 3-hydroxy-and cyclopropane derivatives. These fatty acids are present in lipopolysaccharide, cell wall lipoprotein and lippteichoic acid as well as membrane glycerolipids (Table 3.209). 

Methyl-branched fatty acids occur sometimes in Nature, for example in bacteria, and their solid state behaviour has been investigated in detail (cf. Abrahamsson, 1959a). Two alternatives of accommodating a methyl branch into the close-packing of the molecules have been found. One, called the r-form, is tilted so that the branch is accommodated in the methyl end group gap or carboxyl end group, and an example of this structure is shown in Fig. 8.33. The other alternative, called v-form, makes space for the branch by change of the molecular direction at the branch, so that the molecule is V-shaped. An example of this structure alternative is shown in Fig. 8.34. 

The common carbon sequence in all these molecules has the (CH2CHCH3CH2CH2) architecture. Mycocerosic acid has the formula C32H64O2 (2,4,6,8-tetramethyloctacosanoic acid) and has four branches in the principal chain. Branched fatty acids (the mycolic acids) are found in bacteria belonging to the Mycobacterium-Nocardia-Corynebacterium group. They have often other functional groups in their chain, and should formally belong to the multifunctional fatty acids. 

In anaerobic bacteria, unsaturated fatty acids can be synthesized in the absence of oxygen (Fig. 2.9), but only monoe-noid fatty acids are produced. It seems likely that a branching... 

In most bacterial species C15 fatty acids are present in trace amounts, so their elevated levels (2-3 times higher than any other fatty acid) in propionibacteria can serve as a diagnostic marker. However, this marker should be taken with caution, since the levels of free fatty acids in bacteria depend on media composition, age of culture and the level of vitamin B12 in the cells. Addition of isoleucine to die medium increases the synthesis of anteiso-C s acid by propionibacteria. In the presence of L-leucine they produce more / o-Ci5 acid by decreasing anteiso-C s acid (Moss et al., 1969). In the cells of young active cultures usually the level of straight-chain mono-unsaturated acids (Cie i, Cis i) is higher. The content of mono-unsaturated fatty acids is higher than the branched-chain fatty acids in cultures deficient in vitamin B12. With the cell free extract of C simplex it was shown that vitamin B12 deficit leads to a decrease in the activity of transmethylase system and in the rate of the transformation of mono-unsaturated acids to CHs-branched fatty acids (Fujii and Fukui, 1969). A distinct fatty acid composition was found (Kusano et al., 1997) in P. cyclohexanicum. The major fatty acid was o-cyclohexyl undecanoic acid, while iso- and anteiso-C s, C16, and Cn fatty acids were also present, but in a small amount. 

Branched-chain fatty acids occur widely in nature, but tend to be present as minor components except in bacteria, where they appear to replace unsaturated fatty acids functionaiiy. Usually, the branch consists of a single methyl group, either on the penultimate (/so) or antepenultimate (anteiso) carbon atoms (Figure 2.2). In the biosynthesis of these fatty acids, the primer molecules for chain-elongation by the fatty acid synthetase are 2-methylpropanoic and 2-methylbutanoic acids, respectively. Methyl branches can be found in other positions of the chain (on even-numbered carbon atoms), if methylmalonyl-coenzyme A rather than malonyl-coenzyme A is used in for chain extension this can occur in bacteria and in animal tissues, especially those of ruminant animals, where polymethyl-branched fatty acids even can be synthesised [275]. 

While distinctive long-chain branched fatty acids occur in bacteria, fatty acids with simple methyl branches are encountered most often in... 

A high proportion of odd chain and of various polymethyl-branched fatty acids occurs in the adipose tissue triacylglycerols of sheep and goats when they are fed diets based on cereals such as barley. Cereal starch is fermented by bacteria in the rumen to form propionate, and when the animals capacity to metabolize propionate via methylmalonyl-CoA to succinate is overloaded, propionyl- and methylmalonyl-CoA accumulate. Garton and his colleagues showed that methylmalonyl-CoA can take the place of malonyl-CoA in fatty acid synthesis and that with acetyl- or propionyl-CoA as primers, a whole range of mono-, di- and tri-methyl branched fatty acids can be produced. 

In addition to unsaturated fatty acids, several other modified fatty acids are found in nature. Microorganisms, for example, often contain branched-chain fatty acids, such as tuberculostearic acid (Figure 8.2). When these fatty acids are incorporated in membranes, the methyl group constitutes a local structural perturbation in a manner similar to the double bonds in unsaturated fatty acids (see Chapter 9). Some bacteria also synthesize fatty acids containing cyclic structures such as cyclopropane, cyclopropene, and even cyclopentane rings. 

Suzuki T, K Tanaka, I Matsubara, S Kinoshita (1969) Trehalose lipid and alpha-branched-beta-hydroxy fatty acid formed by bacteria grown on -alkanes. Agric Biol Chem 33 1619-1627. 

Polar lipid fatty acids Branched-chain C35 and C37 acids Bacteria, especially Bacillus spp. 

Maefarlane, G.T., Gibson, G.R., Beatty, J.H., and Cummings, J.H., Estimation of short-chain fatty acid production from protein by human intestinal bacteria based on branched-chain fatty acid measurements, F M5 Mfcroftfo/. Ecol., 101 81-88 (1992). 

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