Characterization of the phospholipid and fatty acid composition of Sendai virus

The Microbe: The Basics of Structure, Morphology, and Physiology as They Relate to Microbial Characterization and Attribution

This chapter is meant to (1) review classical methods used to characterize and classify microbes and (2) introduce new molecular methods used in microbial characterization. The fundamental composition of microbes is discussed as well as their importance in classification of microbes into genus and species. Classical microbiological methods in general seek to define the common features of specific bacterial groups as a means of classification and identification of microbes. Thus, the focus was to describe the common features which discriminated closely related groups of organisms. In contrast, the newer molecular methods often seek to expand the classification of microbes not only as a means to organize microbial phylogeny but also to differentiate signatures between microbes identified within a species in greater detail. Molecular biology tools are used both as an adjunct to established methods and as replacement for classical methods for detection, discrimination, or identification of bacterial and viral species.

Implications for lipids during replication of enveloped viruses

Enveloped viruses, which include many medically important viruses such as human immunodeficiency virus, influenza virus and hepatitis C virus, are intracellular parasites that acquire lipid envelopes from their host cells. Success of replication is intimately linked to their ability to hijack host cell mechanisms, particularly those related to membrane dynamics and lipid metabolism. Despite recent progress, our knowledge of lipid mediated virus-host interactions remains highly incomplete. In addition, diverse experimental systems are used to study different stages of virus replication thus complicating comparisons. This review aims to present a unifying view of the widely diverse strategies used by enveloped viruses at distinct stages of their replication cycles.

Lipid of white-spot syndrome virus originating from host-cell nuclei

The hypothesis that white-spot syndrome virus (WSSV) generates its envelope in the nucleoplasm is based on electron microscopy observations; however, as yet there is no direct evidence for this. In the present study, the lipids of WSSV and the nuclei of its host, the crayfish Procambarus clarkii, were extracted and the neutral lipid and phospholipid contents were analysed by high-performance liquid chromatography, thin-layer chromatography and gas chromatography/mass spectrometry. Phosphatidylcholine (PC) and phosphatidylethanolamine comprised 62.9 and 25.8 %, respectively, of WSSV phospholipids, whereas they comprised 58.5 and 30 %, respectively, of crayfish nuclei phospholipids. These two phospholipids were the dominant phospholipids, and amounts of other phospholipids were very low in the total WSSV and crayfish nuclei phospholipids. The data indicate that the phospholipid profile of WSSV and crayfish nuclei are similar, which is in agreement with the model that the lipids of WSSV are from the host-cell nuclei. However, the fatty acid chains of PC were different between the WSSV virions and crayfish nuclei, and the viral neutral lipid component was also found to be somewhat more complicated than that of the host nuclei. The number of species of cholesterol and hydrocarbon in virus neutral lipid was increased compared with that in host-cell nuclei neutral lipid. It is suggested that the differences between WSSV and its host are either due to selective sequestration of lipids or reflect the fact that the lipid metabolism of the host is changed by WSSV infection.

Oxidation decomposition of unsaturated fatty acids by singlet oxygen in phospholipid bilayer membranes

Oxidation decomposition of unsaturated fatty acids with singlet oxygen generated from a photosensitizing agent was investigated in liposome bilayer membranes under a light irradiation condition. The liposome of which the bilayer membrane was composed of L-alpha-dipalmitoylphosphatidylcholine (DPPC), protoporphyrin IX (PpIX), and an unsaturated fatty acid (oleic acid, linoleic acid, alpha-linolenic acid, or arachidonic acid) were prepared with Bangham's method. In irradiating the liposome dispersion with light ranged from 550 to 750 nm, the unsaturated fatty acid was decomposed through an oxidation reaction with singlet oxygen. The decomposition rate constant was obeyed as the following order: arachidonic acid > oleic acid > alpha-linolenic acid > linoleic acid. This result indicates that oleic acid is readily degraded despite its lower unsaturated degree. In addition, micropolarity and microfluidity of the hydrocarbon region in the liposome bilayer membrane including the unsaturated fatty acid and PpIX decreased with an increase in light irradiation time. These findings suggest that interaction among the hydrocarbon chains of DPPC in the liposome bilayer membrane is promoted by migration of the oxidized unsaturated fatty acid from the hydrocarbon region, leading to form close-packed and well-ordered orientation of the hydrocarbon chains.

Entry mechanisms of enveloped viruses. Implications for fusion of intracellular membranes

Enveloped viruses infect cells by a mechanism involving membrane fusion. This process is mediated and triggered by specific viral membrane glycoproteins. Evidence is accumulating that fusion of intracellular membranes, as occurs during endocytosis and transport between intracellular organelles, also requires the presence of specific proteins. The relevance of elucidating the mechanisms of virus fusion for a better understanding of fusion of intracellular membranes is discussed.