How complex was the first living cell, when it arose some 3.8-4.0 billion years ago? And how complex are the one-celled organisms, living today? Are they primitive? What have some of the world's leading microbiologists found out about this now?
Thomas D. Brock is Professor at the University of Wisconsin. And Michael T. Madigan is Professor at the Southern Illinois University, USA. They write in their textbook Biology of Microorganisms:
"A point that deserves emphasis here is that none of the organisms living today are primitive. All extant life forms are modern organisms, well adapted to, and successful in, their ecological niches. Certain of these organisms may indeed by phenotypically similar to primitive organisms and may represent stems of the evolutionary tree that have not changed for millions of years; in this respect they are related to primitive organisms, but they are not themselves primitive." (1991:684).
Could an archaebacterium, adapted to boiling water, evolve in there into higher forms of life, as evolutionists believe?
Professors Brock and Madigan: "It is not known why archaebacteria are the slowest evolving of the three kingdoms, but it may be related to their inhabiting extreme environments. For example, organisms living in thermal environments must maintain those genes, which specify phenotypic characteristics adapting them to high temperatures; these genes cannot be significantly changed during evolution if the organism is to maintain itself in these environments. Indeed, by ribosomal RNA sequence criteria, organisms like the extremely thermophillic archaebacteria are likely to have been among the earliest life forms. The phenotypic properties of this group, thermophilicity, and anaerobic organotrophy/lithotrophic metabolism, agree well with the phenotype of primitive organisms predicted from a consideration of early earth geochemical conditions." (1991:814).
"Temperature is one of the most important environmental factors influencing the growth and survival of organisms. It can affect living organisms in either of two opposing ways. As temperature rises, chemical and enzymatic reactions in the cell proceed at more rapid rates and growth becomes faster. However, above a certain temperature, proteins, nucleic acids, and other cellular components are sensitive to high temperatures and may be irreversibly denaturated. Usually, therefore, as the temperature is increased within a given range, growth and metabolic functions increase up to a point where inactivation reactions set in. Above this point cell functions fall sharply to zero. Thus we find that for every organism there is a minimum temperature below which growth no longer occurs, an optimum temperature at which growth is most rapid, and a maximum temperature above which growth is not possible.
"The optimum temperature is always nearer the maximum than the minimum. These are temperatures, often called the cardinal temperatures, are general characteristic for each type of organisms, but are not completely fixed, as they can be modified by other factors in the environment." Brock and Madigan (1991:321).
Acidity and Alkalinity (pH)
What does one mean by acidity and alkalinity? How does that affect the one-celled organism?
Professors Brock and Madigan: "Acidity or alkalinity of a solution is expressed by its pH value on a scale in which neutrality is pH 7. Those pH values that are less than 7 are acid and those greater than 7 are alkaline (or basic). It is important to remember that pH is a logarithmic function; a change of one pH unit represents a ten-fold change in hydrogen ion concentration. Thus vinegar (pH near 2) and household ammonia (near pH 11) differ in hydrogen ion concentration by one billion times.
"Each organism has a pH range within which growth is possible, and usually has a well-defined pH optimum. Most natural environments have pH values between 5 and 9, and organisms with optima in this range are most common. Only a few species can grow at pH values of less than 2 or greater than 10. Organisms that live at low pH are called acidophiles. Fungi as a group tend to be more acid-tolerant than bacteria.
"A few organisms can be considered alkalinophilic, because they have high pH optima, sometimes as high as pH 11-12. Alkaliniphilic microorganisms are usually found in high basic habitats such as soda lakes and high-carbonate soils.
"Although most bacteria grow best at neutral pH, acidophilic bacteria also exist. In fact, some of these bacteria are obligate acidophiles, unable to grow at all at neutral pH. Obligately acidophilic bacteria include several species of the eubacterial genus Thiobacillus, and several genera of the archaebacteria, including Sulfolobus and Thermoplasma. Thiobacillus and Sulfolobus exhibit an interesting property: they oxidize sulfide minerals and produce sulfuric acid. ... It is strange to consider that for obligate acidophiles a neutral pH is actually toxic! Probably the most critical factor for obligate acidophily is the plasma membrane. When the pH is raised to neutrality, the plasma membrane of obligate acidophilic bacteria actually dissolves, and the cells lyse (= fall apart), suggesting that high concentrations of hydrogen ions are required for membrane stability."(1991:327, 328).
What are autotrophs? And how do these one-celled organisms live?
Brock and Madigan: "Organisms which use inorganic chemicals or light as energy sources are frequently able to grow in the complete absence of organic materials, using carbon dioxide as their sole source of carbon. The term autotroph (meaning literally, self-feeding) is sometimes applied to organisms able to obtain all of the carbon they need from inorganic sources. Note that autotroph does not refer to the energy source used, but to the carbon source. Autotrophs are of great importance to the functioning of the biosphere because they are able to bring about the synthesis of organic matter from inorganic (nonliving) sources. Because humans and other animals require organic carbon, the life of the biosphere itself is dependent upon the activities of autotrophic organisms. The process by which carbon dioxide is used as a sole carbon source is sometimes called autotrophic CO2 fixation." (1991:562).
Many of the bacteria and archaebacteria, adapted to hot or boiling water, are rather small. Why are they so small? Are the smallest cells the most primitive cells?
Brock and Madigan: "Microorganisms are small, and being small has several physiological advantages. The rate at which nutrients and waste products pass into or out of the cell is in general inversely proportional to cell size; transport rates in turn affect an organism's metabolic rate and growth rate. Thus, the smaller the cell, the faster is its potential growth rate.
"The accumulation of nutrients and elimination of waste products of a cell involves the cell surface, especially the cell membrane. The cytoplasm of the cell, where many essential metabolic activities take place, communicates with the external environment through the cell membrane, and the rate of membrane surface available to transport materials in and out of the cell. That is, a relation exists between cell volume and cell surface area, the latter of which is a good measure of the amount of available membrane.
"However, the relation between volume and surface is not constant. This point may be seen most easily in the case of the sphere, in which the volume is a function of the square of the cube of the radius (V = 4/3 pi x r3) and the surface area is a function of the square of the radius (A = pi x r3). The surface/volume ratio of a sphere can therefore be expressed as 3/r. Thus a smaller sphere (smaller r value) has a higher ratio of surface area to volume than a larger sphere.
"To return to a biological example, a small cell should therefore have more efficient exchange with its surroundings than a large cell. Cell size cannot be reduced indefinitely, however, as a certain minimum volume is necessary for a cell to contain all the genetic information and biochemical apparatus such as enzymes and ribosomes.
"Although most procaryotic cells are small, there is a wide variation in size among different organisms. Most bacteria have distinct cell shapes, which remain more or less constant, although shape can be influenced to some extent by the environment. The shape of a cell definitely affects its ecology. Cocci, for instance, being round, become less distorted upon drying and thus can usually survive more severe desiccation than can rods or spirals. Cocci can exist as individual cells or form regular arrangements of cells. Rods, on the other hand, have more surface exposed per unit volume than cocci, and thus can more readily take up nutrients from dilute solutions. Even square bacteria are known. These unusual organisms are quite distinctive in their straight sides and right-angle corners, such as brines used for commercial production of salt. It is thought that their unusual morphology is related to the stresses they must deal with in their environments because of high salt content." Brock and Madigan (1991:43).
As a cell increases in size, its surface/volume ratio decreases. After T. D. Brock et al. (1991:43). Figure 3.7. The smaller a cell is, the larger its surface, compared to its volume, and the faster it is able to live. Bacteria and archaea living in boiling water – at the limits of life -, for example, must be small. They need a large cell-surface, so that their metabolism can be very high. The volume of the sphere is calculated like this: 4 pi r3/3. And the surface of a sphere of radius r = 4 pi r². It contains also the circle-number pi. This shows us: Information and mathematics do exist independently of mankind: in the world of physics and biology. Information and mathematics always come from an intelligent person: the Creator.
The bacterial and archaeal cell are small, compared to plants and animals. Does this mean, then, that they are primitive, pre-stages in the evolution of life? - Not at all. What have scientists found out now about this?
Wolfgang Fritsche is Professor of Microbiology at the Friedrich-Schiller-University in Jena, East Germany. He believes in evolution and writes: "The natural evolution of the organisms has obviously gone into two directions, into that of miniaturizing and that of complexity. Both strategies of evolution have succeeded, as the coexistence of the pro- and eukaryonts in their natural ecosystems show us. Thus, one should not talk here about lower and higher organisms, but about organisms with a simpler and a more complex organization. The miniaturized organism fulfills very effectively all the criteria of life: self-reproduction, metabolism, and mass transfer, signal reception and -reaction, mobility." (1990:32).
Under the heading "Small cell dimensions - great output", Professor Wolfgang Fritsche then says: "The large ratio of surface to volume permits an intensive interaction with the environment. Microorganisms have an 'extroverted' manner of life. Due to the relatively short transporting distances in the cell, this leads to large metabolic performances. Respiration is a measure of metabolism. The bacteria have a respiration rate (QO2 = µm O2 per 1 mg of cellular dry substance h-1) of about 1 000, yeast of about 100, and animalic and vegetative tissues of about 1-10. For bacterial metabolism, Thiemann (1964) gives us a clear idea.
"A bacterium fermenting lactose, metabolizes within one hour 1 000 to 10 000 times as much substrate, as its own body weight. If a human being wanted to metabolize 1 000 times as much sugar, as his own body weight, he would need about 250 000 hours for this: about half his life." (1990:33, 34).
"Another aspect of the large microbial productivity is its growth. Bacteria like Escherichia coli have under optimal conditions, a generative time of 20 min., yeast, about 2 hrs. In this time, the biomass doubles itself each time. This continuous in an exponential manner... From microbial protein-production, one has calculated: in the fodder-yeast factory with 500 kg protein starting biomass, within 24 hours, 50 000 kg protein can be produced. But a cow, (with a body weight of 500 kg), produces in 24 hours only 0.5 kg protein. The biomass of a young cow doubles itself within 1-2 months, that is, in about 2 000 hours. In summary, we may say here that microorganisms, compared to their biomass, are about 100-1 000 times as productive as plants and animals." Fritsche, W. (1990:34).
That was about yeast. Could you also give an example about the growth of bacterial populations?
Prof. Wolfgang Fritsche: "When the individual cell grows, the cell divides; and the number of cells will then increase, the cell population will grow. It will grow exponentially, out of one cell will become two, out of two, four, and so on. - When a cell divides itself within 30 minutes (generation time 0.5 h): In one hour there are two doublings (dividing rate 2 h). It will keep on growing exponentially, until one food substance becomes too scarce. During the culture methods, commonly used now in microbiology, this limitation for bacteria, growing quickly at an optimal temperature, will be reached within a day. In a culture in a closed system (known as a batch culture), the bacteria will multiply 1 000-100 000fold, for example, from 106 to 1010 cells per ml.
"How fast nutrition will limit exponential growth, a calculation from the textbooks of Stanier et al. (1983) will show us. If a bacterium, with a generative time of 20 min. would multiply exponentially for 48 hours, a mass of 2.2 x 1031 g would be reached. That is about 4 000 times the weight of our earth." (1990:259).
The bacterium is well adapted to its environment. - Why? How does it do that?
Prof. Wolfgang Fritsche: "A microbial kind (of bacterium) is able to adapt itself quickly to many different environmental conditions. This flexibility is one of the strategies of survival of microorganisms. Thus, they are able to survive in their 'extroverted' manner of life the changing environmental conditions. The bacterial cell is so small, that only a few of the enzymes, encoded in its genetic information, do have enough room in it. A set of enzymes, needed for the basic metabolism, is always there. They are called constitutive. The other enzymes are made, when needed. For this, the cells have a very highly developed system for regulating the enzyme synthesis... It permits a very economical utilization of substrates. First, it uses the food substances, coming directly into the cellular metabolism, like amino acids. When they are used up, many microbes are able to synthesize amino acids out of ammonia and sugars. For this, extra enzymes are needed. They are synthesized then under these conditions." Fritsche, W. (1990:34, 35).
The cell is made up of different types of molecules: of nucleic acids and proteins. How complex are they? And in how many different forms can they be made?
James Darnell is Professor at the Rockefeller University. He and his co-workers state in their textbook Molecular Biology: "Nucleic acids are made from four different nucleotides, linked together in chains that may be millions of units long. Because these subunits can be linked in any order, the number of possible nucleic acids n units long is 4n. A 10-unit nucleic acid has 410 (more than 1 million) possible structures; a 100-unit nucleic acid has 4100 (more than 1060).
"The chemical reactions that constitute life processes are directed and controlled by proteins. There are 20 different amino acids in proteins. Thus a 100-unit protein has 20100 (more than 130) possible structures. This enormous variability means that cells and organisms differ greatly in structure and function even though they are constructed of the same types of biopolymers produced by similar chemical reactions." (1990:43, 44).
Why has the first living cell on earth arisen? Why does it exist?
Professor James Darnell and co-workers: "A detailed theory of evolution that would explain how the primitive oligonucleotide-ologopeptide interactions developed into a working translation system is entirely beyond the limits of present knowledge. ... We indicated earlier that absolute conclusions about the nature of the earliest genes or the earliest cells may never be possible." (1990:1056, 1071).
The genetic code and the translation apparatus of the cell: Why have they arisen? How have they arisen?
Prof. James Darnell and co-workers (who believe in evolution): "During precellular evolution two different but coordinated problems had to be solved to enable nucleic acids to store information that could specify proteins. First, a correspondence had to be established between a linear order in one polymer and a linear order in the other - that is, a code had to develop; second, a means of translating the one linear order into the other had to be found. We know that in all cells the present-day three-letter nucleotide code in mRNA fulfills the first of these requirements and that the translation function is carried out by tRNA bound to the ribosome.
"However, the mechanism by which the nucleotide code 'words' were chosen may always remain speculative, because there is no known chemical complementarity between the three nucleotides of a codon and its cognate amino acids." (1990:1131).
Comment: The cell has a four-letter nucleotid-code. Each nucleotide has three letters.
How well is the cell adapted to its environment, for example, to its supply of food? And what has the first living cell eaten?
Frederick C. Neidhardt is Professor at the University of Michigan, Ann Arbor. He and his co-workers state in their textbook Physiology of the Bacterial Cell (1990:418):
"Bacteria are particularly well adapted to exploit their nutritional environment and to convert it into their own special form of selective advantage - high growth rate. To accomplish this remarkable feat, the makeup of a bacterial cell changes profoundly with nutrition-imposed growth rates: both macromolecular composition and cell size change with growth rate. The teleological reason for some of these changes is obvious.
"For example, if a bacterium is to grow faster, it needs more protein-synthesizing machinery to accomplish the task. But unused machinery is always a disadvantageous expense. So, for a bacterial cell to grow at the maximum rate that a particular medium will support, it must contain a precisely set optimal amount of protein-synthesizing machinery - more, or less, would decrease growth rate. In contrast, the physiological advantage of some other growth rate-associated changes - for example, DNA content and cell size - are not so immediately apparent; but, as we shall see, they, too, are essential if the bacterial cell is to take advantage of its nutritional environment. All these changes act coordinately to maximize growth rate of the bacterial cell in the particular environment available to it."
The first bacteria and archaea, made some 3.8-4.0 billion years ago, had to live on inorganic food, like carbon dioxide. Other kinds of bacteria, made after them, were able to live then on the remains of dead bacteria: on organic food. - What is more complicated: to live on inorganic food or on organic food?
Prof. F. C. Neidhardt and co-workers: "Growth on a single source of carbon and energy - a substrate - requires a relatively high cellular level of enzymes that metabolize the substrate and feed the catabolic products into the central fueling pathways, because all metabolic pathways in the cell flow from the metabolites produced by these catabolic enzymes. Bacteria appear able to sense the appropriateness of each catabolic pathway in a given circumstance and to regulate gene expression accordingly." (1990:375).
The living cell is orderly arranged. It is designed for a certain purpose. - Why has this order in the living cell arisen? How has it arisen?
Professor Bruce Alberts and co-workers say in their textbook Molecular Biology of the Cell: "Thousands of different chemical reactions are occurring in a cell at any instant of time. The reactions are all linked together into chains and networks in which the product of one reaction becomes the substrate of the next. Most of the chemical reactions in cells can be roughly classified as being concerned with catabolism or with biosynthesis. Reactions of biosynthesis begin with the intermediate products of glycolis and the citric cycle (and closely related compounds) and generate the larger and more complex molecules of the cell." (1989:71).
Why does the cell make protein? How has the making of protein in the cell arisen?
Prof. Bruce Alberts and co-workers, who believe in evolution: "The molecular processes underlying protein synthesis seem inexplicably complex. Although we can describe many of them, they do not make conceptual sense in the way that DNA transcription, DNA repair, and DNA replication do. As we have seen, protein synthesis in present-day organisms centers on a very large ribonucleoprotein machine, the ribosome, which consists of proteins arranged around a core of rRNA molecules. Why should rRNA molecules exist at all, and how did they come to play such a dominant part in the structure and function of the ribosome? The answer would undoubtedly help us to understand protein synthesis. ... Protein synthesis also relies heavily on a large number of different proteins that are bound in the rRNAs in the ribosome. The complexity of a process with so many different interacting components has made many biologists despair of ever understanding the pathway by which protein synthesis evolved." (1989:219).
How is the cell's gene expression controlled? How does the cell know, when to make how much of what at the right time?
Prof. Bruce Alberts and co-workers: "An organism's DNA sequence encodes all of the RNA and protein molecules that are available to construct its cells. Yet a complete description of the DNA sequence of a genome - be it a few million nucleotides of a bacterium or the 3 billion nucleotides of a human - would provide relatively little understanding of the organism itself. It has been said that the genome represents a complete 'dictionary' for the organism, containing all of the 'words' available for its construction. But we can no more reconstruct a play by Shakespeare from a dictionary of English words. In both cases the problem is to know how the elements in the dictionary are used; the number of possible combinations of elements is so vast that obtaining the dictionary itself is the relatively easy part and only a start toward solving the problem.
"Of course, we are still very far from being able to 'write' an organism from the sequence of its genome. This will require a much more complete understanding of all of cell biology, including knowledge of how the thousands of large and small molecules in a cell behave once they have been synthesized." (1989:219).