Algae: Cell Structure
There are two basic types of cells in the algae, prokaryotic and eukaryotic. Prokaryotic cells lack membrane-bounded organelles (plastids, mitochondria, nuclei, Golgi bodies, and flagella) and occur in the cyanobacteria. The remainder of the algae are eukaryotic and have organelles. A eukaryotic cell is often surrounded by a cell wall composed of poly saccharides that are […]
Phycology
Phycology or algology is the study of the algae. The word phycology is derived from the Greek word phykos, which means “seaweed.” The term algology, described in Webster’s dictionary as the study of the algae, has fallen out of favor because it resembles the term algogenic which means “producing pain.” The algae are thallophytes (plants […]
Bacterial Transduction
It is also a mode of bacterial gene transfer, which is mediated by viruses. It is a frequent mode of horizontal gene transfer in nature. Indeed evidence suggests that the number of genes moved by marine viruses from one host cell to another is huge (perhaps 1024 per year). Furthermore, viruses in marine environments and hot […]
Bacterial Transformation
It is another way, DNA can move between bacteria is through transformation, discovered by Fred Griffith in 1928. Transformation is the uptake by a cell of DNA, either a plasmid or a fragment of linear DNA, from the surroundings and maintenance of the DNA in the recipient in a heritable form. In natural transformation, the […]
Bacterial conjugation
Conjugation, the transfer of DNA by direct cell-to-cell contact, depends on the presence of a conjugative plasmid. Plasmids are small, double-stranded DNA molecules that can exist independently of host chromosomes. They have their own replication origins, replicate autonomously, and are stably inherited. Some plasmids are episomes, plasmids that can exist either with or without being […]
Saccharomyces
About 10-16 species of Saccharomyces are currently recognized. We will focus on S. cerevisiae, which in many ways is the most important fungus yet discovered. About 25 strains of S. cerevisiae exist, and these have different physiological properties which are relevant to their biotechnological applications. Many were formerly regarded as different species. Saccharomyces cerevisiae is the […]
Conidium production in ascomycetes
There are several steps in the production and release of conidia, namely (1) conidiogenesis, i.e. conidial initiation; (2) maturation; (3) delimitation; (4) secession, i.e. separation from the conidiogenous cell; (5) proliferation of the conidiogenous cell or conidiophore to form further conidia. Conidiogenesis occurs in two ways which appear to be distinct at first glance: blastic […]
Conidia of ascomycetes
Conidia: The asexual spores or conidia of ascomycetes are remarkably diverse in form, structure and modes of dispersal, but their development or conidiogenesis occurs in a limited number of ways. The cell from which a conidium develops is the conidiogenous cell and usually one or more such cells are borne on a stalk, the conidiophore. […]
Ascomycota: Life Cycles
Sexual life cycles: Sexual life cycles in the strict sense, i.e. involving nuclear fusion and meiosis, occur only in those ascomycetes which possess asci, because it is within the young ascus that these events occur. Ascospores of most ascomycetes contain one or more haploid nuclei, and therefore most (but by no means all) ascomycetes have a […]
Phytophthora
The name Phytophthora (Gr.: ‘plant destroyer’) is apt, most species being highly destructive plant pathogens. The best known is P. infestans, cause of late blight of potatoes. This fungus is confined to solanaceous hosts (especially tomato and potato), but others have a much wider host range. For example, P. cactorum has been recorded from over […]