The paper “ Are Viruses Alive and Should They Be Classified among Micro-Organisms? ” is a thoughtful example of a literature review on biology. Viruses are the biological objects that have sparked renewed interest following the recent discovery of Mimivirus. At one end, there are those who still hold the traditional view that although they possess some of the properties of living systems such as having a genome, they are actually nonliving infectious entities and should not be considered microorganisms. On the other hand, there are those who argue that they fall in the boundary between life and non-life, organism and non-organism, and biology and chemistry.
A clear distinction in the conceptualization is thus needed. This paper provides insight into the debate; are viruses alive. This will be discussed under the following heading: What is life? There is no precise scientific definition of life, but most observers would agree that life includes certain qualities in addition to an ability to replicate. For some, life is often defined in terms of a list of distinctive properties that distinguish living systems from dead organisms and inanimate matter.
Mickle and Aune (2011) list seven features common in living things described as a description of life. These include homeostasis, complex and cellular organism, ability to reproduce, metabolism, growth, and development, ability to adapt and evolve and, ability to respond to stimulus. This is closely related to the earlier definition by Macklem and Seely(2010) who described life as self-contained, self-regulating, self-organizing, self-reproducing, interconnected, open thermodynamic network of component parts which performs work, existing in a complex regime which combines stability and adaptability in the phase transition between order and chaos, as a plant, animal, fungus, or microbe. Traditional concepts of viruses as non-living (the differences between a virus and a cell)The traditional view conceptualized viruses as quite distinct from cells.
Cells are generally described as membrane-enclosed compartments that contain genomic DNA (chromosomes), molecular machinery for genome replication and expression, a translation system that makes proteins, metabolic and transport systems that supply monomers for these processes, and various regulatory systems (Koonin, 2010). On the other hand, Ahlquist (2006) defines Viruses as generally very small packages of single or double-stranded DNA or RNA often just a few genes, wrapped up in a coating of protein and sometimes an additional lipid envelope.
This is contrary to the earlier definition given by Marc van Regenmortel and Mahyt as any number of concrete objects that possess various relational properties (for instance, its host, vector, and infectivity) that arise by virtue of a relation with other objects (Marc van Regenmortel and Mahyt, 2004). The traditional view of Viruses revolved around the premise that they did not meet all the criteria of the generally accepted definition of life thus excluding them from organismal status.
They were initially thought to be not compost of cell structure or membranes not even cells like bacteria and other living things do, yet this is regarded as the basic unit of life. In addition, they were thought to be unable to metabolize independently and could not replicate and synthesize new products without a host. Instead, they only seemed most lifelike by invading and co-opting the machinery of living cells in order to make more of themselves, often killing their hosts in the process.
They use their hosts, which probably include every organism past and present, or occasionally work in collaboration with other viruses to make necessary enzymes. According to Dupré and O’ Malley (2009) viruses can carry out such biologically impressive activities as entering cells, co-opting the transcription and translation machinery of the cell, and picking up and moving about DNA from the host organisms with which they interact. In view of the two scholars, by exploiting or collaborating with cellular organisms in these ways, viruses very effectively reproduce themselves and have no need for autonomous metabolism (Dupré and O’ Malley, 2009).
Claverie, JM, H Ogata, S Audic, C Abergel, K Shure and PE Fournier(2006) Mimivirus and the emerging concept of ‘giant’ virus. Virus Research 117: 133-144.
Helen Pearson (2008) Virophage suggests viruses are alive Nature 454, 677 7 August 2008)
James E. Mickle and Patricia M. Aune(2011)A Simple, Inexpensive, Dynamic, & Hands-on Exercise for Prompting Discussion of the Characteristics of Living Things The American Biology Teacher Vol. 73, No. 3 (March 2011), pp. 164-166
Jean-Michel Claverie (2006) Viruses take center stage in cellular evolution, Genome Biology, June 2006, 7:110
John Dupré and Maureen A. O’Malley (2009) Varieties of Living Things: Life at the Intersection of Lineage and Metabolism Philos Theor Biol (2009) 1:e003
Koonin, E. V. (2010) The Two Empires and Three Domains of Life in the Postgenomic Age. Nature Education 3(9):27
Marc H. van Regenmortel and Brian W.J. Mahyt (2004) Emerging Issues in Virus Taxonomy Emerging Infectious Diseases Vol. 10, No. 1, January 2004
Peter T. Macklem and Andrew Seely(2010) Towards a Definition of Life: Perspectives in Biology and Medicine, The Johns Hopkins University Press Volume 53, Number 3, Summer 2010, pp. 330-340