Detection and evaluation of different morphological forms of Mycoplasma hominis in human semen

Abstract

Recently discovered microcolonial forms of Mycoplasma hominis ( M. hominis ) and their impact on human spermatogenesis are studied. The spermatozoa of 125 fertile men (sperm donors; from Reprobank [Reproductive Tissue Bank, Moscow, Russia]) and of 93 patients with fertility problems (from the Federal State Budgetary Institution "Research Centre for Medical Genetics [RCMG]", Moscow, Russia) were used. Classical colonies of M. hominis and microcolonies were detected by molecular biological methods, culture of bacteria, and transmission electron microscopy. The unique structure of microcolonial cells, in which the cytoplasmic cylinder is surrounded by concentric electron-dense and electron-light layers with a periodicity of 12-14 nm, and the ability of microcolonial cells to attach to spermatozoa are shown. In patients with lower sperm quality, microcolonies of M. hominis were detected 2.5 times more frequently than classical colonies. The detection of microcolonies in the ejaculate and the frequent isolation of microcolonies from sperm samples of patients with fertility problems suggest that microcolonial cells may be one cause of infertility.

Figure 1

TEM of ultrathin sections of microcolonial cells (MCs). (a) General view of the microcolony of Mycoplasmas. Noticeable interlacing of filamentous elements, which are presented on longitudinal (F) and transverse sections (FS). (b) Longitudinal section through the MC cell. Noticeable striae with a frequency of 12–14 nm. The number of striae is variable. (c) Cross section through the MC cell. Concentric layers with striation size 12–14 nm surround the central space of average electron density with a diameter of approximately 20 nm. (d) Filamentous structure with striae 12–14 nm (FS) was found among classic colony cells. G: a granular form of a classical colony; TEM: transmission electron microscopy.

Figure 2

TEM of ultrathin sections of spermatozoa from the ejaculate, in which CCs were found. (a) Membrane-limited inclusions containing spherical elementary bodies of Mycoplasmas (EB) in the nuclear pocket at the base of the sperm head. (b) Fragment of a. The sperm nuclear pocket containing EB. (c) Binuclear spermatozoon with EB in the cytoplasmic droplet. (d) Fragment of c. EB in cytoplasmic droplet. NE: the nuclear envelope that limits the nuclear pocket; Ch: the sperm chromatin; Fl: the sperm flagellum; A: sperm acrosome; M: mitochondria; TEM: transmission electron microscopy.

Figure 3

TEM of ultrathin sections of semen samples from which Mycoplasmas CCs and MCs were isolated. (a) Destroyed spermatozoon with the elementary bodies of Mycoplasma (EB) spilling out. (b) Fragment of a. Sperm tail of destroyed spermatozoon with the Mycoplasma EB spilling out. (c) Neutrophilic leukocyte with developing (DP) and formed phagosomes (Ph) containing EB. (d) Cross section through the MC cell. Concentric layers with a striation size of about 20 nm surround an electron-dense central space with a diameter of about 80 nm. CCs: classical colonies; MCs: microcolonies; A: acrosome; M: mitochondria of the flagellum; ODF: outer dense fibrils surrounding the axoneme; N: segmented nucleus of a neutrophilic leukocyte; TEM: transmission electron microscopy.

Figure 4

TEM of ultrathin sections of semen samples after Mycoplasma infection. (a) Membrane-limited inclusions, containing structures morphologically identical to Mycoplasma CC cells, are attached to the sperm flagellum (Fl). (b) An In containing elementary bodies of Mycoplasmas was found in seminal fluid. (c) MC cells with a characteristic striation of 12–14 nm are attached to the bacterial cell with a gram-negative cell wall (GN). MC is a longitudinal section through a cell of Mycoplasma MC, TMC is a transverse section through the Mycoplasma cell of MC. (d) The Mycoplasma MC cell is attached to the sperm Fl. TEM: transmission electron microscopy. CC: classical colony; MC: microcolony; EB: the elementary bodies of Mycoplasma; In: membrane-limited inclusion.