Spore formation

In general, an adverse environment, and in particular the absence or limited presence of one component, induces spore formation. Examples of such components are alanine, Zn, Fe, POj and, in the case of the aerobic (oxygen-requiring) Bacillus species, oxygen. Equally, certain substances, for instance Ca and Mn, have to be present for the process of spore formation to proceed to completion. 

If the conditions for spore formation are fulfilled the sequence of events shown in Fig. 1.9 occurs. 

The bulk of evidence indicates the existence of a close relationship between spore formation and the exhaustion of nutrients essential for continued vegetative growth. Sporulation is a defense mechanism to protect the cell when the occasion arises. 

Spore formation is limited almost entirely to two genera of rodshaped bacteria Bacillus (aerobic or facultatively anaerobic), and Clostridium (anaerobic or aerotolerant). With one possible exception, the common spherical bacteria do not sporulate. Some spore-bearing species can be made to lose their ability to produce spores. When the ability to produce spores is once lost, it is seldom regained. SporMation is not a process to increase bacterial numbers because a cell rarely produces more than one spore. 

Signs Chlorotic stripes or overall yellowing on the leaves. Leaves may acquire a downy appearance. Spore formation is more abundant on the lower surface. As the plant ages, leaves may narrow, become abnormally erect, and appear somewhat dried out. Tassels may be malformed. Ears may be aborted. Early affected plants are stunted. 

Sporozoa in which spore formation ends the individual life of the organism. 

II Sporozoa- in which spore formation occurs during the vegetative stages of the organism. 

The overall life cycle of a particular yeast Saccharomyces (S.) cerevisiae, is summarised in Fig. S.6 which shows how it is possible for the cells to fuse to form various cell and spore types. The figure shows the possible types of reproduction in yeast. Generally, industrial strains of S. cerevisiae, brewers yeast, reproduce by budding/ fission processes and only sporulate under specialised conditions. However, many strains of yeast are capable of cell fusion to form spores or cells with increased genetic complements. Such strains have many sets of chromosomes and are termed polyploid. Active fermentation of industrial strains involves growth by mitotic division and nutrient depletion which results in stationary cells with little or no spore formation. 

Spore Formation Some bacteria form spores when growth ceases due to starvation or other causes. Spores are more resistant than normal cells to heat, drying, radiation, and chemicals. Spores can remain alive for many years however, they can convert back to normal cells at proper conditions. Spore-forming bacteria are found most commonly in the soil. 

Encapsulation of haustoria could also be seen after curative fungicide treatment. Primary haustoria usually were not encased but all haustoria produced during and after the treatment were distinctly encapsulated, causing a complete inhibition of fungal growth and blocking spore formation. 

Cell division Binary fission, budding, spore formation by a few Mitosis (or meiosis)... 

All these data suggested that PolyPs are very important for the development of fungi, especially spore formation and germination. Tables 8.4-8.6 and Figures 8.27 and 8.28 show the changes in PolyP content at different stages of development in some fungi. 

The prototypical lantibiotic, nisin, was discovered in 1928 for its antibacterial properties and has been used as a preservative in dairy products since the 1950s (1). Nisin and other lantibiotics exhibit nanomolar efficacy against many Gram-positive strains of bacteria (2), which include methicillin resistant Staphylococcus aureus, vancomycin resistant enterococci, and oxacillin resistant bacteria. On the other hand, some lantibiotics function as morphogenetic peptides rather than antibiotics and are important for spore formation in streptomycetes (3). Since the structural elucidation of nisin in the early 1970s, extensive research efforts have been directed at understanding the biosynthesis and mode of action of various lantibiotics. 

Pig. 126.—Yeast, Saccharomyces cerevisice, the variety known as brewers bottom yeast a, spore formation b, elongated cells. After Schneider, Pharmaceutical Bacteriology.)... 

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