Microbial phospholipids

Watts, E.E., Dean, P.A.W. and Martin, R.R. (2002) P nuclear magnetic resonance study of sediment microbial phospholipids. Canadian Journal of Analytical Sciences and Spectroscopy 47, 127-1 33. 

Virtue, P., Nichols, P.D. and Boon, P.l. (1996) Simultaneous estimation of microbial phospholipid fatty acids and diether lipids by capillary gas chromatography. Journal of Microbiological Methods 25, 177-1 85. 

Incorporation of K -acetate into microbial lipids is a simple, yet useful technique for measuring heterotrophic microbial activity. The rate of acetate incorporation into microbial phospholipids has been shown to be an accurate and sensitive measure of growth in sediment samples [37]. The technique has been used to measure activity in sewsige sludge [38], marine sediments [39], antarctic rock microbiota [40], and soils [41]. Acetate incorporation has also been used to sussess the effects of toxicants, both inorgsmic and organic, on microbial metabolic activity [42]. 

The second type of material includes spores, which may or may not produce disease symptoms but which can germinate in the insect gut and give rise to vegetative bacterial cells which in turn may produce, and exoenzymes such as phospholipases (lecithinases) or hyaluronidase. The phospholipases may produce direct toxic symptoms owing to their action on nervous or other phospholipid-containing tissue. Hyaluronidase breaks down hyaluronic acid and produces effects on animal tissue which are morphologically similar to the breakdown of insect gut wall in the presence of microbial insecticide preparations. 

Phosphatidylcholine, commonly known as lecithin, is the most commonly occurring in natnre and consists of two fatty add moieties in each molecule. Phosphati-dylethanolamine, also known as cephahn, consists of an amine gronp that can be methylated to form other compounds. This is also one of the abundant phospholipids of animal, plant, and microbial origin. Phosphatidylserine, which has weakly acidic properties and is found in the brain tissues of mammals, is found in small amounts in microorganisms. Recent health claims indicate that phosphatidylserine can be used as a brain food for early Alzheimer s disease patients and for patients with cognitive dysfunctions. Lysophospholipids consist of only one fatty acid moiety attached either to sn-1 or sn-2 position in each molecule, and some of them are quite soluble in water. Lysophosphatidylchohne, lysophosphatidylserine, and lysophos-phatidylethanolamine are found in animal tissues in trace amounts, and they are mainly hydrolytic products of phospholipids. 

Quantitative estimates of microbial and community structure by means of analysis of the phospholipid fraction have been performed on. sediments, water (135), and dust (136) as well as. soil (137-141). The method is applicable to the study of mixed populations of varying degrees of complexity and is relatively straightforward to perform. A selection of studies involving the analysis of fatty acid profiles of environmental samples are outlined in Table 6. 

N. Ragendran, O. Matsuda. N. Imamura, and Y. Urushigawa, Variation in microbial biomass and community structure in sediments of eutrophic bays as determined by phospholipid ester-linked fatty acids, Appl. Environ. Microbiol. 58 562 (1992). 

Zelles L (1999) Fatty acid patterns of phospholipids and lipopolysaccharides in the characterization of microbial communities in soil a review. Biol Fertil Soils 29 111-129... 

Frostegard A, Tunlid A, Baath E (1993) Phospholipids fatty acid composition, biomass, and activity of microbial communities from two soil types experimentally exposed to different heavy metals. Appl Environ Microbiol 59 3605-3617... 

Pennanen T (2001) Microbial communities in boreal coniferous forest humus exposed to heavy metals and changes in soil pH a summary of the use of phospholipids fatty acids, Biolog and H-thymidine incorporation methods in field studies. Geoderma 100 91-126... 

Fenchel T, King G, Blackburn FI (1998) Bacterial biogeochemistry the ecophysiology of mineral cycling. Academic Press, London, UK Francl LJ (1993) Multivariate analysis of selected edaphic factors and their relationship to Heterodera glycines population density. J Nematol 25 270-276 Frostegard A, Tunlid A, Baath E (1993) Phospholipid fatty acid composition, biomass, and activity of microbial comunities from two soil types experimentally exposed to different heavy metals. Appl Environ Microbiol 59 3605-3617... 

Bossio DA, Scow KM, Gunapala N, Graham KJ (1998) Determinants of soil microbial communities Effects of agricultural management, season, and soil type on phospholipid fatty acid profiles. Microb Ecol 36 1-12... 

The studies on phospholipid bilayers with defined amounts of charged component are helpful to explain the partition characteristics in biological membranes. Liposome water partition data of propranolol in lipids from kidney epithelial cells (a common model system in pharmaceutical sciences for the uptake into the gastrointestinal tract) have been successfully described with partition models developed for pure bilayers or defined mixtures [159]. Since lipophilic cations and anions can be used as probes for the membrane potential, their interaction with microbial and mitochondrial membranes has been studied... 

In addition to the differences in phospholipid content between microbial and host cell membranes, it has been demonstrated that disparity exists between the transmembrane potentials of both organisms. The transmembrane potential is defined by the proton flux between the inner and outer bilayers of the cytoplasmic membrane and ranges from —90 to —110 mV in normal mammalian cells in contrast to transmembrane potentials of —130 to —150mV for logarithmic phase microbes. The differences in these electrochemical gradients have been postulated to drive the influx of peptides into the cell and thus act as a crucial barrier for defining host defense peptide selectivity. ... 

As host defense peptides are membrane-active molecules, safety mechanisms must be employed to avoid deleterious contacts with host cells. These mechanisms may involve the limitation of peptide activation to specific environments or niche-specific amplification. That most ct-helical peptides remain unstructured in aqueous solution and undergo conformational transitions to an activated state within hydrophobic environments supports this postulate. It has also been postulated that the order of anionic phospholipids in microbial plasma membranes likely induces optimal periodicity of polar residues within host defense peptides at the membrane surface. ... 

The organic treatment had higher microbial biomass C and N, enzyme activity and potentially mineralisable N (Cunapala and Scow 1998) and different microbial community composition phospholipid fatty acid than the conventional treatment (Bossio ef al. 1 998). There were minimal differences between treatments in residue decomposition (Cunapala et al. 1998). Cover crops and higher irrigation frequency in the organic treatment may have contributed to the differences (Cunapala and Scow 1998). 

Hay and Morrison (1971) did not neglect the alkyl and alkenyl ethers in milk phospholipids, finding 4% of the latter in phosphatidylethanolamine and 1.3% in phosphatidylcholine. Trans isomers were not found. The authors postulated that the branched chain compounds in the alkenyl ethers were derived from rumen microbial lipids. 

Frostegard, A., Baath, E., and Tunlid, A. (1993). Shifts in the structure of soil microbial communities in limed forests as revealed by phospholipid fatty-acid analysis. Soil Biol. Biochem. 25, 723-730. 

Sundh, I., Nilsson, M., and Borga, P. (1997). Variation in microbial community structure in two boreal peatlands as determined by analysis of phospholipid fatty acid profiles. Appl. Environ. Microbiol. 63,1476-1482. 

---